compositor-{drm, wayland, x11}: remove useless tests for ->supports

Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

src/compositor-drm.c

@@ -1396,8 +1396,7 @@ drm_compositor_create_gl_renderer(struct drm_compositor *ec)
 {
 	EGLint format;
 
-	if (!gl_renderer->supports ||
-	    gl_renderer->supports(&ec->base, "gbm") < 0) {
+	if (gl_renderer->supports(&ec->base, "gbm") < 0) {
 		return -1;
 	}
 

src/compositor-wayland.c

@@ -1962,8 +1962,7 @@ wayland_compositor_create(struct wl_display *display, int use_pixman,
 	}
 
 	if (!c->use_pixman) {
-		if (!gl_renderer->supports ||
-		    gl_renderer->supports(&c->base, "wayland") < 0) {
+		if (gl_renderer->supports(&c->base, "wayland") < 0) {
 			weston_log("No support for "
 			           "EGL_{KHR,EXT,MESA}_platform_wayland; "
 			           "falling back to pixman.\n");

src/compositor-x11.c

@@ -1492,7 +1492,7 @@ init_gl_renderer(struct x11_compositor *c)
 	if (!gl_renderer)
 		return -1;
 
-	if (!gl_renderer->supports || gl_renderer->supports(&c->base, "x11") < 0)
+	if (gl_renderer->supports(&c->base, "x11") < 0)
 		return -1;
 
 	ret = gl_renderer->create(&c->base, EGL_PLATFORM_X11_KHR, (void *) c->dpy,