regulator: Add bindings for TPS62864x

Add bindings for the TPS62864/TPS6286/TPS62868/TPS62869 voltage
regulators.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20220204155241.576342-2-vincent.whitchurch@axis.com


Signed-off-by: Mark Brown <broonie@kernel.org>