pinctrl: sh-pfc: r8a77990: Add support for pull-up only pins
The R-Car Gen3 HardWare Manual Errata for Rev. 1.00 (Jul 2, 2018) states
that the USB30_OVC pin supports pull-up only. It has a bit assigned in
the pull-enable register (PUEN5), but not in the pull-up/down control
register (PUD5).
Add a check for this, to prevent configuring a prohibited setting.