wl1271: Remove REF_CLK hack

This hack was totally wrong and was "needed" because of a problem in the way
we were sending the GENERAL_PARMS command to the firmware.  Now that that
problem has been fixed, this hack can be removed.

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