treewide: dts: Remove default-state=off property from all gpio LED nodes

>From the Documentation/devicetree/bindings/leds/common.txt:

- default-state : The initial state of the LED. Valid values are "on", "off",
  and "keep". If the LED is already on or off and the default-state property is
  set the to same value, then no glitch should be produced where the LED
  momentarily turns off (or on). The "keep" setting will keep the LED at
  whatever its current state is, without producing a glitch.  The default is
  off if this property is not present.

So setting the default-state of the LEDs to `off` is redundant as `off`
is default LED state anyway. We should remove it as almost every new
PR/patch submission contains this property by default which seems to be
just copy&paste from some DTS file already present in the tree.

Signed-off-by: Petr Štetiar <ynezz@true.cz>