ath10k: configure and enable the wakeup capability

ACPI will rely on device driver to tell it if the device could support
wakeup function when system in D3 state.

This has caused some platform can't support remote wakeup correctly,
because the ACPI wakeup GPE is not enabled, hence registers the .set_wakeup
callback to handle it if device supports wakeup.

Tested with QCA6174 hw3.0, firmware ('WLAN.RM.4.4.1-00008-QCARMSWP-1')

Signed-off-by: Ryan Hsu <ryanhsu@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>