regulator: rpi-panel: Handle I2C errors/timing to the Atmel

regulator: rpi-panel: Handle I2C errors/timing to the Atmel

[ Upstream commit 5665eee7a3800430e7dc3ef6f25722476b603186 ]

The Atmel is doing some things in the I2C ISR, during which
period it will not respond to further commands. This is
particularly true of the POWERON command.

Increase delays appropriately, and retry should I2C errors be
reported.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>
Link: https://lore.kernel.org/r/20220124220129.158891-3-detlev.casanova@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>