Bring over AR5416 specific RX filter get/set routines.

Bring over AR5416 specific RX filter get/set routines.

This in particular fixes radar PHY handling - on the AR5212
NIC, one enables the AR_PHY_ERR_RADAR bit in AR_PHY_ERR;
the AR5416 and later also needs a bit set in AR_RX_FILTER.

A follow-up commit is needed to convert the AR5416 ANI code
to use this particular method, as it's currently using the
AR5212 methods directly.

Obtained from:	Atheros
Approved by:	re (kib)