video: fbdev: mb862xx: remove set but not used variable 'mdr'

Fix the following gcc warning:

drivers/video/fbdev/mb862xx/mb862xxfb_accel.c:187:6: warning: variable
‘mdr’ set but not used [-Wunused-but-set-variable]
  int mdr;
      ^~~
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200403022553.33320-1-yanaijie@huawei.com

drivers/video/fbdev/mb862xx/mb862xxfb_accel.c

@@ -184,7 +184,6 @@ static void mb86290fb_imageblit16(u32 *cmd, u16 step, u16 dx, u16 dy,
 static void mb86290fb_imageblit(struct fb_info *info,
 				const struct fb_image *image)
 {
-	int mdr;
 	u32 *cmd = NULL;
 	void (*cmdfn) (u32 *, u16, u16, u16, u16, u16, u32, u32,
 		       const struct fb_image *, struct fb_info *) = NULL;
@@ -196,7 +195,6 @@ static void mb86290fb_imageblit(struct fb_info *info,
 	u16 dx = image->dx, dy = image->dy;
 	int x2, y2, vxres, vyres;
 
-	mdr = (GDC_ROP_COPY << 9);
 	x2 = image->dx + image->width;
 	y2 = image->dy + image->height;
 	vxres = info->var.xres_virtual;