GFS2: use depends instead of select in kconfig

Avoids having to duplicate the dependencies of what is 'select'ed (and on
down...)

Those dependencies are currently incomplete, leading to broken builds with
GFS2_FS_LOCKING_DLM=y and IP_SCTP=n.

Signed-off-by: Benjamin Poirier <bpoirier@suse.de>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>