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.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>