jbd2: add missing MODULE_DESCRIPTION()

Fix the 'make W=1' warning:
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/jbd2/jbd2.o

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20240526-md-fs-jbd2-v1-1-7bba6665327d@quicinc.com>