ipq806x: clean up dts files

ipq806x: clean up dts files

Set the pinmux to the values found in the GPL tarballs of the boards.
Remove pinmux which are is not used (like nand pinmux for spi
flash boards).

This allows to use the wan orange led of the C2600 which had a wrong
pinmux before. Might fix buttons or leds of other boards as well.

Fix the LED color and the ledswitch key code of the C2600. Rename the
ledgnr to ledswitch.

Add support for indication the boot state using LEDs to the D7800,
NBG6817, R7500 and R7500v2.

Change GPIO active to readable values in D7800, EA8500, R7500,
R7500v2 and R7800.

Change gpioexport to gpio pinmux.

Add proper "drive strenght" to i2c4_pins and use it for RPM on
C2600, D7800, EA8500, R7500, R7500v2.

Remove pcie pinmux from D7800.

Move pinctrl to correct place in NBG6817 and R7800.

Signed-off-by: Henryk Heisig <hyniu@o2.pl>