media: dw9807-vcm: The device is not active initially

The probe calls pm_runtime_set_active in the probe, but
has never called dw9807_vcm_resume.
Without a regulator this causes no issue as it just
instructs the VCM to move to the idle position and power
down. With a regulator the pm_runtime_idle calls
dw9807_vcm_suspend, and we get a mismatch in the regulator framework.

Make the active state conditional on having a regulator.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>