wl1271: Add support for acx_pm_config

This acx configures host clock parameters in correspondence with the clock
request line - the settling time of the clock, and whether fast wake-up is
supported.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>