drm/gem-framebuffer: Don't validate buffer size when non-linear

pitch*height does not necessarily equate to buffer size if the
buffer is non-linear, so the buffer validation is invalid.

Disable it for non-linear buffers.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

Author: 6by9

drivers/gpu/drm/drm_gem_framebuffer_helper.c

@@ -182,6 +182,9 @@ int drm_gem_fb_init_with_funcs(struct drm_device *dev,
 			goto err_gem_object_put;
 		}
 
+		if (mode_cmd->modifier[i] != DRM_FORMAT_MOD_LINEAR)
+			continue;
+
 		min_size = (height - 1) * mode_cmd->pitches[i]
 			 + drm_format_info_min_pitch(info, i, width)
 			 + mode_cmd->offsets[i];