media: camss: Add regulator_bulk support

Add the ability to enable or disable multiple regulators in bulk with
camss. This is useful for sm8250, sdm845 and it looks like sdm660 where we
have more than one CSI regulator to do at once.

It should just work for standalone existing vdda regulators and parts which
don't have an explicitly defined CSI regulator.

[hverkuil: fix camss-csid.c:163:13: warning: 'ret' may be used uninitialized in this function]

Reported-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>