Add support for the Lantiq XWAY family of Mips24KEc SoCs.

* Danube (PSB50702)
* Twinpass (PSB4000)
* AR9 (PSB50802)
* Amazon SE (PSB5061)

The Amazon SE is a lightweight SoC and has no PCI as well as a different
clock. We split the code out into seperate files to handle this.

The GPIO pins on the SoCs are multi function and there are several bits
we can use to configure the pins. To be as compatible as possible to
GPIOLIB we add a function

int lq_gpio_request(unsigned int pin, unsigned int alt0,
        unsigned int alt1, unsigned int dir, const char *name);

which lets you configure the 2 "alternate function" bits. This way drivers like
PCI can make use of GPIOLIB without a cubersome wrapper.

The PLL code inside arch/mips/lantiq/xway/clk-xway.c is voodoo to me. It was
taken from a 2.4.20 source tree and was never really changed by me since then.
Signed-off-by: NJohn Crispin <blogic@openwrt.org>
Signed-off-by: NRalph Hempel <ralph.hempel@lantiq.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2249/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Add initial support for Mips based SoCs made by Lantiq. This series will add
support for the XWAY family.

The series allows booting a minimal system using a initramfs or NOR. Missing
drivers and support for Amazon and GPON family will be provided in a later
series.

[Ralf: Remove some cargo cult programming and fixed formatting.]
Signed-off-by: NJohn Crispin <blogic@openwrt.org>
Signed-off-by: NRalph Hempel <ralph.hempel@lantiq.com>
Signed-off-by: NDavid Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2252/
Patchwork: https://patchwork.linux-mips.org/patch/2371/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>