drm/hisilicon/kirin: Set GEM CMA functions with DRM_GEM_CMA_DRIVER_OPS

DRM_GEM_CMA_DRIVER_OPS sets the functions in struct drm_driver
to their defaults. No functional changes are made.

v2:
	* use DRM_GEM_CMA_DRIVER_OPS

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: John Stultz <john.stultz@linaro.org>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Cc: Xu YiPing <xuyiping@hisilicon.com>
Cc: Rongrong Zou <zourongrong@gmail.com>
Cc: Xinliang Liu <z.liuxinliang@hisilicon.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200605073247.4057-15-tzimmermann@suse.de