arm: remove the hack for loading vmlinux images

arm: remove the hack for loading vmlinux images

Don't adjust the RAM location/size when loading an ELF for dom0.  It
was vmlinux specific and no longer needed because Linux can be loaded
from a zImage.  Support for loading ELF images is not removed as it
may be useful for loading things other than the Linux kernel.

This also makes preparing the device tree for dom0 easier.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>