ath79: fix various dts warnings

ath79: fix various dts warnings

ar9344_openmesh_mr600-v1.dts:40.10-44.5: Warning (gpios_property):
/leds-ath9k/wifi2g: Missing property '#gpio-cells' in node
/ahb/pcie-controller@180c0000/wifi@0,0 or bad phandle
=> added gpio-controller + #gpio-cells

qca955x_zyxel_nbg6x16.dtsi:121.3-13: Warning (reg_format):
/ahb/usb@1b000000/port@1:reg: property has invalid length (4 bytes)
(#address-cells == 2, #size-cells == 1)
../dts/qca955x_zyxel_nbg6x16.dtsi:131.3-13: Warning (reg_format):
/ahb/usb@1b400000/port@1:reg: property has invalid length (4 bytes)
(#address-cells == 2, #size-cells == 1)
qca955x_zyxel_nbg6x16.dtsi:120.20-123.4: Warning (avoid_default_addr_size):
/ahb/usb@1b000000/port@1: Relying on default #address-cells value
=> ath79's usb-nodes are missing the address- and size-cells properties.
These are needed for usb led trigger support.

ar7242_ubnt_sw.dtsi:54.4-14: Warning (reg_format): /gpio_spi/gpio_spi@0:reg:
property has invalid length (4 bytes) (#address-cells == 1, #size-cells == 1)
=> the #address-cells and #size-cells had to be nudged.

qca9531_dlink_dch-g020-a1.dts:19.6-39.4: Warning (i2c_bus_bridge):
/i2c: incorrect #size-cells for I2C bus
=> #size-cells = <0>;

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>