fix(cros-bootkernel/x86_64_defconfig_boot) build in the Xen modules

The boot kernel shouldn't have kernel modules, otherwise it will be a
two-step build process for the whole kernel/initrd package, so just
build in the Xen modules to the kernel image itself.
fix(cros-bootkernel/x86_64_defconfig_boot) disable netfilter the like

The bootkernel doesn't need netfilter, and some other networking kernel
modules to be enabled, as all this kernel needs to do is to find the
root partitions and then boot them.  So disable those kernel options
entirely.
fix(cros-bootkernel/x86_64_defconfig_boot) remove some network modules

There are a number of network protocols not needed for the boot kernel.
As these were being built as modules, just remove them, they are not
needed.
fix(cros-bootkernel/x86_64_defconfig_boot) disable SELINUX

The boot kernel only needs the default Linux security model, so disable
SELinux and the other kernel security models.
fix(cros-bootkernel/x86_64_defconfig_boot) disable network filesystems

The boot kernel is not going to have to find a network filesystem, so
just disable those entirely.
fix(cros-bootkernel/x86_64_defconfig_boot) disable some filesystems

The boot kernel does not need aufs, xfs, btrfs, or vfat, so disable them
all.
fix(cros-bootkernel/x86_64_defconfig_boot) disable ext2 and ext3

The ext4 filesystem can handle both of these types of images, so only
build it, and not the others.
fix(cros-bootkernel/x86_64_defconfig_boot) disable FUSE and PSTORE

These two options are not needed in a boot kernel.
fix(cros-bootkernel/x86_64_defconfig_boot) enable HYPERV

Always build in the HYPERV modules and core to the bootkernel, as they
will be needed when booting on a Hyper-V system.
fix(cros-bootkernel/x86_64_defconfig_boot) disable some more network modules

The boot kernel does not care about bonding, tun/tap, or some other
minor network modules, so disable them.
fix(cros-bootkernel/x86_64_defconfig_boot) disable DRM

The boot kernel does not need DRM, so disable it.
fix(cros-bootkernel/x86_64_defconfig_boot) disable ISCSI

The boot kernel does not need ISCSI, so disable it.
fix(cros-bootkernel/x86_64_defconfig_boot) more config cleanups

Build in a few ACPI drivers, and remove some hardware-specific drivers
that the boot kernel will never see.

Also disable CONFIG_WATCHDOG, as the boot kernel should never be alive
long enough for a watchdog to need to kick in.
fix(cros-bootkernel/x86_64_defconfig_boot) disable CONFIG_ETHERNET

No ethernet drivers are needed for the boot kernel, so disable them all.
fix(cros-bootkernel/x86_64_defconfig_boot) build in VIRTIO drivers

The VIRTIO drivers should be built into the boot kernel.

Also disable OPENVSWITCH, as that is not needed in the boot kernel.
fix(cros-bootkernel/x86_64_defconfig_boot) disable HOTPLUG_PCI

The boot kernel does not need HOTPLUG_PCI, so disable it, and the video
output control option.
fix(cros-bootkernel/x86_64_defconfig_boot) disable CONFIG_I2C

I2C is not needed for the boot kernel, so disable it, removing a bunch of
build options and modules.
fix(cros-bootkernel/x86_64_defconfig_boot) disable ACPI_HED and NETPRIO_CGROUP

Neither of these options are needed for the boot kernel, so disable
them.
fix(cros-bootkernel/x86_64_defconfig_boot) disable CONFIG_PPS

This is no longer needed for the boot kernels, as we disabled ethernet
devices.
fix(cros-bootkernel/x86_64_defconfig_boot) disable unneeded crypto modules

Now that the ethernet drivers are gone, we can disable a number of the
crypto modules that are no longer needed.