uml: don't use a too long string literal

uml uses a concatenated string literal to store the contents of .config,
but .config file content is varaible, it can be very long.

Use an array of string literals instead.

Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>