Bluetooth: hci_qca: Optimized code while enabling clocks for BT SOC

* Directly passing clock pointer to clock code without checking for NULL
  as clock code takes care of it
* Removed the comment which was not necessary
* Updated code for return in qca_regulator_enable()

Signed-off-by: Venkata Lakshmi Narayana Gubba <gubbaven@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>