media: camss: Set unused regulators to the empty set

If a CAMSS block has no regulator set the regulator array to the empty set
as opposed to setting the first element of the array to NULL.

Suggested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>