MAINTAINERS: add cpumask and nodemask files to BITMAP_API

cpumask and nodemask APIs are thin wrappers around basic bitmap API, and
corresponding files are not formally maintained. This patch adds them to
BITMAP_API section, so that bitmap folks would have closer look at it.
Signed-off-by: Yury Norov <yury.norov@gmail.com>

MAINTAINERS

@@ -3504,10 +3504,14 @@ R:	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
 R:	Rasmus Villemoes <linux@rasmusvillemoes.dk>
 S:	Maintained
 F:	include/linux/bitmap.h
+F:	include/linux/cpumask.h
 F:	include/linux/find.h
+F:	include/linux/nodemask.h
 F:	lib/bitmap.c
+F:	lib/cpumask.c
 F:	lib/find_bit.c
 F:	lib/find_bit_benchmark.c
+F:	lib/nodemask.c
 F:	lib/test_bitmap.c
 F:	tools/include/linux/bitmap.h
 F:	tools/include/linux/find.h