render/egl: stop relying on platform for high priority

All backends use the GBM platform. We can't use it to figure out
whether the DRM backend is used anymore.

Let's just try to always request a high-priority EGL context. Failing
to do so is not fatal.

render/egl.c

@@ -324,9 +324,9 @@ struct wlr_egl *wlr_egl_create(EGLenum platform, void *remote_display) {
 	attribs[atti++] = EGL_CONTEXT_CLIENT_VERSION;
 	attribs[atti++] = 2;
 
-	// On DRM, request a high priority context if possible
+	// Request a high priority context if possible
-	bool request_high_priority = ext_context_priority &&
+	// TODO: only do this if we're running as the DRM master
-		platform == EGL_PLATFORM_GBM_MESA;
+	bool request_high_priority = ext_context_priority;
 
 	// Try to reschedule all of our rendering to be completed first. If it
 	// fails, it will fallback to the default priority (MEDIUM).