Add definition of the POCCTRL register and bits therein to R8A77990 E3
pincontrol driver. This allows the pincontrol driver to configure SDHI
pin voltage according to power-source DT property.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>