ramips: fix dtc compiler warnings

ramips: fix dtc compiler warnings

The latest dtc compiler considers nodes named i2c or spi as the
respective bus:

  /pinctrl/i2c: incorrect #address-cells for I2C bus
  /pinctrl/spi: incorrect #address-cells for SPI bus

Rename the node to fix the false positives.

Fix the spi node unit address for the DWR-512-B and UBNT-ER-e50 to get
rid of the following warning:

  SPI bus unit address format error, expected "n"

Signed-off-by: Mathias Kresin <dev@kresin.me>
(backported from ffa55386f17cff29f6c3ffbe873335511e253932)