regulator: add warning flags

Add 'warning' level events and error flags to regulator core.
Current regulator core notifications are used to inform consumers
about errors where HW is misbehaving in such way it is assumed to
be broken/unrecoverable.

There are PMICs which are designed for system(s) that may have use
for regulator indications sent before HW is damaged so that some
board/consumer specific recovery-event can be performed while
continuing most of the normal operations.

Add new WARNING level events and notifications to be used for
that purpose.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/9b54aa5589ae4b5945d53d114bac3fae55fa4818.1622628333.git.matti.vaittinen@fi.rohmeurope.com


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