[GFS2] Fix bug in Makefiles for lock modules

The Makefile had the wrong CONFIG_ variable in it so that in
case GFS2 was y and the lock modules were m, they were not
getting built properly.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/locking/dlm/Makefile

-obj-$(CONFIG_GFS2_FS) += lock_dlm.o
+obj-$(CONFIG_GFS2_FS_LOCKING_DLM) += lock_dlm.o
 lock_dlm-y := lock.o main.o mount.o sysfs.o thread.o plock.o
 

fs/gfs2/locking/nolock/Makefile

-obj-$(CONFIG_GFS2_FS) += lock_nolock.o
+obj-$(CONFIG_GFS2_FS_LOCKING_NOLOCK) += lock_nolock.o
 lock_nolock-y := main.o