siphash: add missing MODULE_DESCRIPTION() macro

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/siphash_kunit.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.

Link: https://lkml.kernel.org/r/20240531-md-lib-siphash_kunit-v1-1-38688065b796@quicinc.comSigned-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/siphash_kunit.c

@@ -194,4 +194,5 @@ static struct kunit_suite siphash_test_suite = {
 kunit_test_suite(siphash_test_suite);
 
 MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");
+MODULE_DESCRIPTION("Test cases for siphash.c");
 MODULE_LICENSE("Dual BSD/GPL");