st/mesa: Also use PIPE_FORMAT_R8G8B8A8_SRGB for framebuffer_sRGB.

When running virgl on a GLES host the only sRGB formats that support
rendering is RGBA and RGBX. That pipe format is in the sRGB default
lists that the state tracker uses when mapping mesa formats.

Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Jakob Bornecrantz <jakob@collabora.com>

src/mesa/state_tracker/st_extensions.c

@@ -711,7 +711,8 @@ void st_init_extensions(struct pipe_screen *screen,
 
       { { o(EXT_framebuffer_sRGB) },
         { PIPE_FORMAT_A8B8G8R8_SRGB,
-          PIPE_FORMAT_B8G8R8A8_SRGB },
+          PIPE_FORMAT_B8G8R8A8_SRGB,
+          PIPE_FORMAT_R8G8B8A8_SRGB },
          GL_TRUE }, /* at least one format must be supported */
 
       { { o(EXT_packed_float) },