Zero out fields as needed by hardware reduced mode

There are a large number of FADT fields and flags that are ignored
in hardware reduced mode ACPI (used by AArch64).  This cleans out
those fields by setting them to zero so they will not be used by
accident.  Further, this removes a couple of ACPI boot warnings
about broken firmware reported by the Linux kernel where it indicated
invalid field lengths for fields that should have been zero in the
first place.

This increments the FADT OEM revision number, too, to note the change.

Signed-off-by: Al Stone <ahs3@redhat.com>
[Foundation] Create a dummy DeviceTree.c to fix build error

ArmPlatformPkg/Bds/Bds.inf wants to unconditionally build
a hardcoded source file:

  ../APMXGenePkg/DeviceTree/DeviceTree.c

Foundation isn't using devicetree anymore, so create an empty
DeviceTree.c file from the Makefile when building for foundation
to avoid build error in Bds module. This worked before because
a DeviceTree.c was inadvertantly checked in to the tree. It has
since been removed.

Signed-off-by: Mark Salter <msalter@redhat.com>
Add .gitignore for DeviceTree build droppings

Signed-off-by: Mark Salter <msalter@redhat.com>
fix PrePeiCoreEntryPoint

Remove an APM change which prevents models from initializing
exception handlers. APM does this elsewhere, but not sure why
they commented out the parts they did. There shouldn't be any
harm in running this code on Mustang and it boots fine in its
original form.

Signed-off-by: Mark Salter <msalter@redhat.com>
Merge branch 'apm-scratch' of git+ssh://git.engineering.redhat.com/srv/git/users/astone/linaro-edk2 into apm-scratch