arm:manage versioning of u-boot and upgrade u-boot

Replaced the wget download of u-boot by a versioned git checkout
this allows us to better manage the u-boot and MLO version we ship
while still allowing us to build ofline.

This changes replaces the BASE_URL setting by U_BOOT_BIN_DIR and
also updates to a newer build of u-boot.
arm:refactor replace cmdline.txt by bootargs passed to the kernel.

Put the boot arguments in uEnv.txt and not in cmdline.txt to allow
a more dynamic configuration of the system. We now also pass the
u-boot board_name parameter to the kernel.
arm:determine board_id using bootargs.board_name

On startup determine the board_id based on the board name
passed from u-boot. This code also export "board" for use
by  userland using sysenv.

Change-Id: I1064a49497c82b06f50d98650132bc0a7f543568
arm:switch to dynamic configuration for the kernel.

During startup machine.board_id is now determined. The kernel can now
at runtime determine how to configure itself and does so.

Change-Id: I4f615af9bfa5add219e618b911a51af127591d6a
arm:replace ifdef's by runtime checks in the i2c driver.

Change-Id: I5cdff48d8be9bbe5a4734192b451dc45983fbef2
arm:make the kernel server and driver binaries identical.

Make the kernel server and driver binaries indentical for the different
ARM platforms. We no longer need to define the AM335X or DM37XX flags
during compilation. The remaining differences are all located in u-boot.

Change-Id: I14ac60837dd2d7f116bc5fa56d3989b48d7c4fea
arm:refactor move pagetable to the common directory.

Change-Id: Ic3178241f86156f729f016017f61017653ddbd23
arm:disable filemmap.

We currently have a few of the POSIX tests failing because filemmap
is enabled by default. The working assumption is that these program
pass a pointer to the file server that points to a not yet loaded
data segment. When the file server tries to access that data it
therefore generates a pagefault and a call to itself it can not
handle because it is unable to first return the current call.

Change-Id: Ic1a2d9cd0a542bd950e2b08accb61cfe2855c5a3
arm:indenting

Change-Id: I2f8f664fa4c66649db8981e58e6bb7a6f533df5a
VM bugfix & regression test

The bug in the offset correction code for the 'shrink region from
below' case can easily case an assert(foundregion->offset == offset)
to trigger (if the blocks are touched afterwards, e.g. on fork())
as the offsets become wrong. This commit is a fix & regression test.

Change-Id: I28ed403e3891362a2dea674a49e786d3450d2983