MAINTAINERS: add crc_kunit.c back to CRC LIBRARY

Restore lib/tests/crc_kunit.c to CRC LIBRARY following the rename in
commit db6fe4d61e ("lib: Move KUnit tests into tests/ subdirectory")
which made it no longer match the file pattern lib/crc*.

Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20250511052151.420228-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

MAINTAINERS

@@ -6253,6 +6253,7 @@ F:	Documentation/staging/crc*
 F:	arch/*/lib/crc*
 F:	include/linux/crc*
 F:	lib/crc*
+F:	lib/tests/crc_kunit.c
 F:	scripts/gen-crc-consts.py
 
 CREATIVE SB0540