Bluetooth: hci_qca: Don't vote for specific voltage

Devices with specific voltage requirements should not request voltage
from the driver, but instead rely on the system configuration to define
appropriate voltages for each rail.

This ensures that PMIC and board variations are accounted for, something
that the 0.1V range in the hci_qca driver currently tries to address.
But on the Lenovo Yoga C630 (with wcn3990) vddch0 is 3.1V, which means
the driver will fail to set the voltage.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>