gfs2: Remove 'first' trace_gfs2_promote argument

Remove the 'first' argument of trace_gfs2_promote: with GL_SKIP, the
'first' holder isn't the one that instantiates the glock
(gl_instantiate), which is what the 'first' flag was apparently supposed
to indicate.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>