drm/mga/mga_state: Remove unused variable 'buf_priv'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/mga/mga_state.c: In function ‘mga_dma_iload’:
 drivers/gpu/drm/mga/mga_state.c:945:22: warning: variable ‘buf_priv’ set but not used [-Wunused-but-set-variable]

Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: by <jhartmann@precisioninsight.com>
Cc: Jeff Hartmann <jhartmann@valinux.com>
Cc: Keith Whitwell <keith@tungstengraphics.com>
Cc: Gareth Hughes <gareth@valinux.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201106214949.2042120-6-lee.jones@linaro.org

drivers/gpu/drm/mga/mga_state.c

@@ -942,7 +942,6 @@ static int mga_dma_iload(struct drm_device *dev, void *data, struct drm_file *fi
 	struct drm_device_dma *dma = dev->dma;
 	drm_mga_private_t *dev_priv = dev->dev_private;
 	struct drm_buf *buf;
-	drm_mga_buf_priv_t *buf_priv;
 	drm_mga_iload_t *iload = data;
 	DRM_DEBUG("\n");
 
@@ -959,7 +958,6 @@ static int mga_dma_iload(struct drm_device *dev, void *data, struct drm_file *fi
 		return -EINVAL;
 
 	buf = dma->buflist[iload->idx];
-	buf_priv = buf->dev_private;
 
 	if (mga_verify_iload(dev_priv, iload->dstorg, iload->length)) {
 		mga_freelist_put(dev, buf);