MIPS: ralink: fix MT7628 pinmux typos

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Cc: john@phrozen.org
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13306/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>