msm: rotator: Pass device pointers to regulator_get()

Passing a device pointer instead of NULL as the first argument
to regulator_get() allows the device to be taken into
account when finding a matching regulator. This removes the need
to specify a unique regulator_name in platform data.

Change-Id: Id16f85866c94b3f3b57aa720cdfbdcf3e2fd241d
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>