[PATCH] uml: build cleanups

Fix a build failure when CONFIG_MODE_SKAS is disabled and make a Makefile
comment fit in 80 columns.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>