Bluetooth: hci_qca: Use regulator bulk enable/disable

With the regulator_set_load() and regulator_set_voltage() out of the
enable/disable code paths the code can now use the standard
regulator bulk enable/disable API.

By cloning num_vregs into struct qca_power there's no need to lug around
a reference to the struct qca_vreg_data, which further simplifies
qca_power_setup().

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