ext4: add missing MODULE_DESCRIPTION()

Fix the 'make W=1' warning:
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/ext4/ext4-inode-test.o
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20240527-md-fs-ext4-v1-1-07aad5936bb1@quicinc.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/inode-test.c

@@ -279,4 +279,5 @@ static struct kunit_suite ext4_inode_test_suite = {
 
 kunit_test_suites(&ext4_inode_test_suite);
 
+MODULE_DESCRIPTION("KUnit test of ext4 inode timestamp decoding");
 MODULE_LICENSE("GPL v2");