pinctrl: spacemit: support I/O power domain configuration

pinctrl: spacemit: support I/O power domain configuration

Dual-voltage GPIO banks default to 3.3V operation. Even when a bank is
externally supplied with 1.8V, the internal logic remains in the 3.3V
domain, leading to functional failures.

Add support for programming the IO domain power control registers to
allow explicit configuration for 1.8V operation.

These registers are secure due to hardware safety constraints.
Specifically, configuring the domain for 1.8V while externally supplying
3.3V causes back-powering and potential pin damage. Consequently, access
requires unlocking the AIB Secure Access Register (ASAR) in the APBC
block before any read or write operation.

Signed-off-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>