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.

Reported-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Fixes: 83f6941a ("pinctrl: sh-pfc: r8a77990: Add bias pinconf support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>