power: smb135x-charger: add pinctrl support for smb135x

In some targets, smb135x driver needs to configure some pins through
pinctrl. Hence add this support.

Change-Id: I8f2c305904e9d8a1c822203c1a82722c1a7fc9eb
Signed-off-by: Ke Liu <keliu@codeaurora.org>