ath10k: improve the firmware download time for QCA6174

ath10k: improve the firmware download time for QCA6174

Len Brown reported the system resume time is taking more than 2 seconds in
bug - https://bugzilla.kernel.org/show_bug.cgi?id=185621.

The reason of the 2 seconds is due to the firmware download time.

The chip is booted up in the default reference clock speed to handle the
firmware download to chip memory and advanced to the support higher speed
clock to run the firmware after all. The default reference clock in the
hardware is slow so that the firmware download time is taking up to 2
seconds for a 600KB firmware file.

	[76796.349701] ath10k_pci : boot uploading firmware image len 688691
	[76798.334612] ath10k_pci : htt tx max num pending tx 1056

The resolution here is to enable the higher speed clock if the hardware
supported before the firmware download at BMI stage, so that the hardware
can handle the firmare download in a more efficient way. This can help to
improve the firmware download time from 2 seconds to around 500ms for the
same 600KB firmware file.

	[322858.577919] ath10k_pci boot uploading firmware image len 688691
	[322859.093094] ath10k_pci htt tx max num pending tx 1056

The steps to advance to the higher speed clock is very hardware specific,
so adding the hardware ops for the hardware that can support this.

Reported-by: Len Brown <lenb@kernel.org>
Tested-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Ryan Hsu <ryanhsu@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>