drm/exynos: Drop drm_gem_prime_export

They're the default. We can't do the same on the import side, due to
the exynos_drm->dma_dev not necessarily matching the overall drm
device.

Aside: Would be really nice to switch the others over to
drm_gem_object_funcs.
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Joonyoung Shim <jy0922.shim@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190614203615.12639-15-daniel.vetter@ffwll.ch

drivers/gpu/drm/exynos/exynos_drm_drv.c

@@ -124,7 +124,6 @@ static struct drm_driver exynos_drm_driver = {
 	.dumb_create		= exynos_drm_gem_dumb_create,
 	.prime_handle_to_fd	= drm_gem_prime_handle_to_fd,
 	.prime_fd_to_handle	= drm_gem_prime_fd_to_handle,
-	.gem_prime_export	= drm_gem_prime_export,
 	.gem_prime_import	= exynos_drm_gem_prime_import,
 	.gem_prime_get_sg_table	= exynos_drm_gem_prime_get_sg_table,
 	.gem_prime_import_sg_table	= exynos_drm_gem_prime_import_sg_table,