examples/egl_common: switch rgba format

The current ARGB2101010 has really "corase" control over the alpha.
Particularily, examples/layer-shell would look really strange with certain
parameters. For examples, when passing an alpha of 0.84, the box would not
appear transparent at all anymore.

Patched as suggested by @mstoeckl -- thank you!

examples/egl_common.c

@@ -20,10 +20,10 @@ PFNEGLCREATEPLATFORMWINDOWSURFACEEXTPROC eglCreatePlatformWindowSurfaceEXT;
 
 const EGLint config_attribs[] = {
 	EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
-	EGL_RED_SIZE, 1,
+	EGL_RED_SIZE, 8,
-	EGL_GREEN_SIZE, 1,
+	EGL_GREEN_SIZE, 8,
-	EGL_BLUE_SIZE, 1,
+	EGL_BLUE_SIZE, 8,
-	EGL_ALPHA_SIZE, 1,
+	EGL_ALPHA_SIZE, 8,
 	EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
 	EGL_NONE,
 };