MAINTAINERS: add ASLR maintainer

Since achieving the full ASLR by merging the PIE randomization in commit
cc503c1b ("x86: PIE executable randomization"), I have been dealing with
most (if not all) of the bugreports reported against userspace address
space randomization, so it might be a good idea to provide a decent
contact point in MAINTAINERS.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>