lib/cpumask_kunit: add tests file to MAINTAINERS

cpumask related files are listed under the BITMAP API section, so the
file with tests for cpumask should be added to that list.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
Reviewed-by: David Gow <davidgow@google.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>

Author: svanheule

MAINTAINERS

@@ -3612,6 +3612,7 @@ F:	include/linux/find.h
 F:	include/linux/nodemask.h
 F:	lib/bitmap.c
 F:	lib/cpumask.c
+F:	lib/cpumask_kunit.c
 F:	lib/find_bit.c
 F:	lib/find_bit_benchmark.c
 F:	lib/test_bitmap.c