NOMMU: Don't check vm_region::vm_start is page aligned in add_nommu_region()

Don't check vm_region::vm_start is page aligned in add_nommu_region() because
the region may reflect some non-page-aligned mapped file, such as could be
obtained from RomFS XIP.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>