[U-Boot] rockchip: rk3288: Add support for drive-strength in PINCTRL

[Philipp Tomsich]

> Currently, drive-strenght to 12ma are described and supposed to be used
> on RK3288. However, the pinctrl driver for this SoC only handles muxing
> and pull up/pull down via PU/PD control registers. So complex IPs like
> GMAC are working in normal ethernet 100mbps, but not at 1gbps typically.
> 
> This commit adds support for handling drive-strength of 12ma, when it's
> defined in the DT.
> 
> Signed-off-by: Romain Perier <romain.perier at collabora.com>
> Acked-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> ---
>  drivers/pinctrl/rockchip/pinctrl_rk3288.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 

Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>