procfs: clean up proc_reg_get_unmapped_area for 80-column limit

Clean up proc_reg_get_unmapped_area due to its 80-column limit
violation.

Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Tested-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>