drm_driver.fops can't be shared since the owner then becomes tinydrm.ko.
Move the fops declaration to the driver.

v2: Use DEFINE_DRM_GEM_CMA_FOPS
Reported-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170326142529.16938-1-noralf@tronnes.org