pinctrl: renesas: Implement unlock register masks

The V3U SoC has several unlock registers, one per register group. They
reside at offset zero in each 0x200 bytes-sized block.

To avoid adding yet another table to the PFC implementation, this
patch adds the option to specify an address mask instead of the fixed
address in sh_pfc_soc_info::unlock_reg.

This is a direct port of Linux 5.12 commit e127ef2ed0a6
("pinctrl: renesas: Implement unlock register masks") by
Ulrich Hecht <uli+renesas@fpond.eu>

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>