simple-egl: Don't set-up alpha for opaque/fullscreen

When setting the window as opaque or fullscreen (which creates an opaque
region) make it so we don't have any alpha pixels set.
This was mistakenly dropped from a previous patch series update to
simple-egl.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

clients/simple-egl.c

@@ -488,7 +488,10 @@ redraw(void *data, struct wl_callback *callback, uint32_t time)
 	glUniformMatrix4fv(window->gl.rotation_uniform, 1, GL_FALSE,
 			   (GLfloat *) rotation);
 
-	glClearColor(0.0, 0.0, 0.0, 0.5);
+	if (window->opaque || window->fullscreen)
+		glClearColor(0.0, 0.0, 0.0, 1);
+	else
+		glClearColor(0.0, 0.0, 0.0, 0.5);
 	glClear(GL_COLOR_BUFFER_BIT);
 
 	glVertexAttribPointer(window->gl.pos, 2, GL_FLOAT, GL_FALSE, 0, verts);