efi_loader: efi_allocate_pages is too restrictive

When running on the sandbox the stack is not necessarily at a higher memory
address than the highest free memory.

There is no reason why the checking of the highest memory address should be
more restrictive for EFI_ALLOCATE_ANY_PAGES than for
EFI_ALLOCATE_MAX_ADDRESS.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
[agraf: use -1ULL instead]
Signed-off-by: Alexander Graf <agraf@suse.de>