dlm: Make name input parameter of {,dlm_}new_lockspace() const

| fs/gfs2/lock_dlm.c:207: warning: passing argument 1 of 'dlm_new_lockspace' discards qualifiers from pointer target type

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: David Teigland <teigland@redhat.com>