render: add missing arg to wlr_renderer_impl.get_buffer_caps

The types of buffers supported by the renderer might depend on the
renderer's instance. For instance, a renderer might only support
DMA-BUFs if the necessary EGL extensions are available.

Pass the wlr_renderer to get_buffer_caps so that the renderer can
perform such checks.

Fixes: 982498fab3 ("render: introduce renderer_get_render_buffer_caps")

render/pixman/renderer.c

@@ -510,7 +510,7 @@ static bool pixman_read_pixels(struct wlr_renderer *wlr_renderer,
 	return true;
 }
 
-static uint32_t pixman_get_render_buffer_caps(void) {
+static uint32_t pixman_get_render_buffer_caps(struct wlr_renderer *renderer) {
 	return WLR_BUFFER_CAP_DATA_PTR;
 }