mesa/main: GL_GEOMETRY_SHADER_INVOCATIONS exists in GL_OES_geometry_shader

It seems that for desktop GL this was included with ARB_gpu_shader5, but
for OpenGL ES this is already included with the base extension and there is
a CTS test that checks this.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
diff --git a/src/mesa/main/shaderapi.c b/src/mesa/main/shaderapi.c
index 0a9700a..8bca17a 100644
--- a/src/mesa/main/shaderapi.c
+++ b/src/mesa/main/shaderapi.c
@@ -833,8 +833,10 @@
       }
       return;
    case GL_GEOMETRY_SHADER_INVOCATIONS:
-      if (!has_gs || !ctx->Extensions.ARB_gpu_shader5)
+      if (!has_gs ||
+          (_mesa_is_desktop_gl(ctx) && !ctx->Extensions.ARB_gpu_shader5)) {
          break;
+      }
       if (check_gs_query(ctx, shProg)) {
          *params = shProg->_LinkedShaders[MESA_SHADER_GEOMETRY]->
             Program->info.gs.invocations;