drm/nouveau/fbcon/g80: reduce PUSH_SPACE alloc, fire ring on accel init

Only 58 words get written to the ring, not 59. Also, normalize the accel
init wrt nvc0 and nv04 fbcon impls by firing the ring at accel init time
rather than waiting until "later".

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>