brcmsmac: change lcnphy receive i/q calibration routine

The gain level control for the test tone has been changed. This
calbration test tone is used to determine the i/q compensation.
The i/q calibration routine has been reworked to accomodate this.

Cc: Jonas Gorski <jogo@openwrt.org>
Tested-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>