Bluetooth: hci_qca: Split qca_power_setup()

Split and rename qca_power_setup() in order to simplify each code path
and to clarify that it is unrelated to qca_power_off() and
qca_power_setup().

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