ARM: dts: armada-xp: Use pwm-fan rather than gpio-fan

The mvebu GPIO driver can also perform PWM on some pins. Use the pwm-fan
driver to control the fan of the WRT1900AC, giving us finer grained control
over its speed and hence noise.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
URL: https://patchwork.ozlabs.org/patch/427291/


[Ralph Sennhauser: drop flags paramter from pwms, no longer used]
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>