lantiq: Switch to the new SPI driver

lantiq: Switch to the new SPI driver

Compared to the "old" driver:
- Each device must assign a pinctrl setting to the SPI node to allow the
  new SPI driver to configure the SPI pins.
  While here we are also using separate input and output settings so we
  are independent of whether the bootloader configures the pins correctly.
- We use the new "compatible" strings to make the driver choose the
  correct number of chip-selects for each SoC.
- The new driver starts counting the chip-selects at 1 (instead of 0, like
  the old one did). Thus we have to adjust the devices accordingly.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@48293 3c298f89-4303-0410-b956-a3cf2f4a3e73