mesa: allow unsized formats GL_RG, GL_RED for GLES 3.0 with half float

v2: && -> ||, we enable on gles3 or if ARB_texture_rg is enabled

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90748
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/main/glformats.c

@@ -1678,6 +1678,10 @@ _mesa_error_check_format_and_type(const struct gl_context *ctx,
       case GL_LUMINANCE:
       case GL_ALPHA:
          return GL_NO_ERROR;
+      case GL_RG:
+      case GL_RED:
+	 if (_mesa_is_gles3(ctx) || ctx->Extensions.ARB_texture_rg)
+            return GL_NO_ERROR;
       default:
          return GL_INVALID_OPERATION;
       }