drm/omap: Remove set but not used variable 'plane'

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

drivers/gpu/drm/omapdrm/omap_fb.c: In function omap_framebuffer_update_scanout:
drivers/gpu/drm/omapdrm/omap_fb.c:130:16: warning: variable plane set but not used [-Wunused-but-set-variable]

It is not used since commit 2ecceeb5 ("drm/omap:
Move buffer pitch/offset to drm_framebuffer")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1570518949-47574-2-git-send-email-zhengbin13@huawei.com

drivers/gpu/drm/omapdrm/omap_fb.c

@@ -135,7 +135,6 @@ void omap_framebuffer_update_scanout(struct drm_framebuffer *fb,
 {
 	struct omap_framebuffer *omap_fb = to_omap_framebuffer(fb);
 	const struct drm_format_info *format = omap_fb->format;
-	struct plane *plane = &omap_fb->planes[0];
 	u32 x, y, orient = 0;
 
 	info->fourcc = fb->format->format;
@@ -209,8 +208,6 @@ void omap_framebuffer_update_scanout(struct drm_framebuffer *fb,
 	info->screen_width /= format->cpp[0];
 
 	if (fb->format->format == DRM_FORMAT_NV12) {
-		plane = &omap_fb->planes[1];
-
 		if (info->rotation_type == OMAP_DSS_ROT_TILER) {
 			WARN_ON(!(omap_gem_flags(fb->obj[1]) & OMAP_BO_TILED_MASK));
 			omap_gem_rotated_dma_addr(fb->obj[1], orient, x/2, y/2,