Certain SoCs have to program DRV register to configure driving
strength so that we add it in the existing path as an option.
Signed-off-by: Ryder.Lee <ryder.lee@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>