regulator: rpi-panel-v2: Add regulator for 7" Raspberry Pi 720x1280

regulator: rpi-panel-v2: Add regulator for 7" Raspberry Pi 720x1280

Add regulator for the 7" Raspberry Pi 720x1280 DSI panel based on ili9881.
This is the Raspberry Pi DSI Panel V2. The newer Raspberry Pi 5" and 7"
panels have a slightly different register map to the original one. Add a
new driver for this "regulator" chip, this time by exposing two GPIOs and
one PWM controller, both of which can be consumed by panel driver and
pwm-backlight respectively.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Link: https://patch.msgid.link/20250609000748.1665219-2-marek.vasut+renesas@mailbox.org
Signed-off-by: Mark Brown <broonie@kernel.org>