MAINTAINERS: update SCX200 file pattern

commit 3b3da9d2 ("x86: Move scx200 to platform") moved it, convert the
pattern too.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>