Revert "Revert "efi_loader: efi_allocate_pages is too restrictive""

This reverts commit ccfc78b8.

Now that the underlying issue is fixed, we can revert the revert and hence
restore the original EFI code.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Alexander Graf <agraf@suse.de>