x86, mm: Use clamp_t() in init_range_memory_mapping

save some lines, and make code more readable.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-42-git-send-email-yinghai@kernel.org


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>