drm/amdgpu: fix one warning message

In function 'amdgpu_uvd_cs_pass2':
warning: 'min_ctx_size' may be used uninitialized in this function
  buf_sizes[0x4] = min_ctx_size;
                 ^
note: 'min_ctx_size' was declared here
  unsigned image_size, tmp, min_dpb_size, num_dpb_buffer, min_ctx_size;
                                                          ^
Signed-off-by: Jammy Zhou <Jammy.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c

@@ -374,7 +374,8 @@ static int amdgpu_uvd_cs_msg_decode(uint32_t *msg, unsigned buf_sizes[])
 	unsigned height_in_mb = ALIGN(height / 16, 2);
 	unsigned fs_in_mb = width_in_mb * height_in_mb;
 
-	unsigned image_size, tmp, min_dpb_size, num_dpb_buffer, min_ctx_size;
+	unsigned image_size, tmp, min_dpb_size, num_dpb_buffer;
+	unsigned min_ctx_size = 0;
 
 	image_size = width * height;
 	image_size += image_size / 2;