Enable slow diversity combining for the AR9285.

Now that I understand what's going on - and the RX antenna array maps
to what the receive LNA configuration actually is - I feel comfortable
in enabling this.

If people do have issues with this, there's enough debugging now available
that we have a chance to diagnose it without writing it up as 'weird
crap.'

Tested:

* AR9285 STA w/ diversity combining enabled in EEPROM

TODO:

* (More) testing in hostap mode

sys/dev/ath/ath_hal/ar9002/ar9285_phy.c

@@ -87,8 +87,10 @@ ar9285_check_div_comb(struct ath_hal *ah)
 	HAL_EEPROM_v4k *ee = AH_PRIVATE(ah)->ah_eeprom;
         const MODAL_EEP4K_HEADER *pModal = &ee->ee_base.modalHeader;
 
+#if 0
 	/* For now, simply disable this until it's better debugged. -adrian */
 	return AH_FALSE;
+#endif
 
 	if (! AR_SREV_KITE(ah))
 		return AH_FALSE;