drm/nouveau: Add getparam for current PTIMER time.

This will be useful for computing GPU-CPU latency, including
GL_ARB_timer_query extension.

Signed-off-by: Marcin Kościelnicki <koriakin@0x04.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --cc drivers/gpu/drm/nouveau/nouveau_state.c
Simple merge

diff --cc include/drm/nouveau_drm.h
Simple merge