[IA64] Update efi.c and rework xenheap location

[IA64] Update efi.c and rework xenheap location

This is a port of a newer upsteam efi.c to xen/ia64.  For the most
part, this patch is simply incorporating this upstream linux-ia64
patch into the tree:

http://www.kernel.org/hg/linux-2.6/?cs=fb781f6d3e81

To support this new code, xensetup needed to be modified to relocate
the dom0 kernel and initrd images without using efi_memmap_walk() as
this can no longer be called until after reserve_memory().  The dom0
kernel and initrd images are now only moved if necessary and the xen
MDT entry is expanded to cover the xenheap area and any relocated dom0
bits.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>