ipq40xx: rt-ac58u: fix device-tree snafu

ipq40xx: rt-ac58u: fix device-tree snafu

 - make the device userspace integration (WIFI,MAC,sysupgrade)
   work again by renaming the ubi to UBI_DEV as a temporary measure.
   In the future, once 4.14 support is dropped, this can all be
   refactored again. *sigh*

 - use the wifi0 and wifi1 labels

 - follow Device-Tree Release v0.2 2.2.2 Generic Names Recommendation

 - fix duplicated partition node-names

 - remove qcom,ipq4019 platform compatible. it's no longer needed
   (and wrong because the chip is a qcom,ipq4018).

Fixes: 4c67f3ad78d ("ipq40xx: Adapt 4.19 DTS for upstream SPI-NAND driver")
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>