MAINTAINERS: update it913x patterns

Commit d7104bff ("[media] MAINTAINERS: add
drivers/media/tuners/it913x*") used the incorrect file patterns.  Fix
it.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Antti Palosaari <crope@iki.fi>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>