mesa: check for extension instead of desktop GL

If we ever decide to allow this extension for GLES, this will make life
easier.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8028>

src/mesa/main/pixelstore.c

@@ -94,7 +94,7 @@ pixel_storei(GLenum pname, GLint param, bool no_error)
          ctx->Pack.Alignment = param;
          break;
       case GL_PACK_INVERT_MESA:
-         if (!no_error && !_mesa_is_desktop_gl(ctx))
+         if (!no_error && !_mesa_has_MESA_pack_invert(ctx))
             goto invalid_enum_error;
          ctx->Pack.Invert = param;
          break;