MIPS: lantiq: Add a GPHY driver which uses the RCU syscon-mfd

Compared to the old xrx200_phy_fw driver the new version has multiple
enhancements. The name of the firmware files does not have to be added
to all .dts files anymore - one now configures the GPHY mode (FE or GE)
instead. Each GPHY can now also boot separate firmware (thus mixing of
GE and FE GPHYs is now possible).
The new implementation is based on the RCU syscon-mfd and uses the
reeset_controller framework instead of raw RCU register reads/writes.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: john@phrozen.org
Cc: p.zabel@pengutronix.de
Cc: kishon@ti.com
Cc: mark.rutland@arm.com
Cc: linux-mips@linux-mips.org
Cc: linux-mtd@lists.infradead.org
Cc: linux-watchdog@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-spi@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17128/


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