ath6kl: Check wmi ready event status before validating abi version

There is no point to check firmware ABI version when the driver
fails to wait for WMI_READY event during the boot time.

For such failures, the driver should assume the firmware is not
booted and start doing cleanup.

Signed-off-by: Raja Mani <rmani@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>