drm: Remove set but not used variable 'gem'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/gpu/drm/vc4/vc4_txp.c: In function 'vc4_txp_connector_atomic_check':
drivers/gpu/drm/vc4/vc4_txp.c:252:29: warning:
 variable 'gem' set but not used [-Wunused-but-set-variable]
  struct drm_gem_cma_object *gem;
                             ^
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190215033507.103232-1-yuehaibing@huawei.comSigned-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

drivers/gpu/drm/vc4/vc4_txp.c

@@ -249,7 +249,6 @@ static int vc4_txp_connector_atomic_check(struct drm_connector *conn,
 					struct drm_connector_state *conn_state)
 {
 	struct drm_crtc_state *crtc_state;
-	struct drm_gem_cma_object *gem;
 	struct drm_framebuffer *fb;
 	int i;
 
@@ -275,8 +274,6 @@ static int vc4_txp_connector_atomic_check(struct drm_connector *conn,
 	if (i == ARRAY_SIZE(drm_fmts))
 		return -EINVAL;
 
-	gem = drm_fb_cma_get_gem_obj(fb, 0);
-
 	/* Pitch must be aligned on 16 bytes. */
 	if (fb->pitches[0] & GENMASK(3, 0))
 		return -EINVAL;