drm/v3d/v3d_drv: Remove unused static variable 'v3d_v3d_pm_ops'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/v3d/v3d_drv.c:73:32: warning: ‘v3d_v3d_pm_ops’ defined but not used [-Wunused-const-variable=]

Cc: Eric Anholt <eric@anholt.net>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201116174112.1833368-35-lee.jones@linaro.org