SERIAL: MIPS: lantiq: implement OF support

Add devicetree and handling for our new clkdev clocks. The patch is rather
straightforward. .of_match_table is set and the 3 irqs are now loaded from the
devicetree.

This series converts the lantiq target to clkdev amongst other things. The
driver needs to handle two clocks now. The fpi bus clock used to derive the
divider and the clock gate needed on some socs to make the secondary port work.

Signed-off-by: John Crispin <blogic@openwrt.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Cox <alan@linux.intel.com>
Cc: linux-serial@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3809/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>