rt2800: add rt2800_rx_filter_calibration procedure

Add procedure for both bands filter calibration and use it on individual
chipset init rfcsr subroutines.

Remove "Set back to initial state" code for 3290 since vendor driver
DPO_RT3290_LinuxSTA_V2600_20120508 does not include it.

Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>