ath9k_hw: Fix hw reset failure with HTC driver

The following commit removed DISABLE_REGWRITE_BUFFER ops. The unnecessary
REGWRITE_BUFFER_FLUSH was not removed properly which is causing failure on
hw reset.

Author: Felix Fietkau <nbd@openwrt.org>
Date:   Tue Oct 5 12:03:42 2010 +0200

    ath9k_hw: clean up register write buffering
Signed-off-by: NRajkumar Manoharan <rmanoharan@atheros.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/mac.c

@@ -491,8 +491,6 @@ bool ath9k_hw_resettxqueue(struct ath_hw *ah, u32 q)
 	REG_WRITE(ah, AR_DMISC(q),
 		  AR_D_MISC_CW_BKOFF_EN | AR_D_MISC_FRAG_WAIT_EN | 0x2);
 
-	REGWRITE_BUFFER_FLUSH(ah);
-
 	if (qi->tqi_cbrPeriod) {
 		REG_WRITE(ah, AR_QCBRCFG(q),
 			  SM(qi->tqi_cbrPeriod, AR_Q_CBRCFG_INTERVAL) |
@@ -508,8 +506,6 @@ bool ath9k_hw_resettxqueue(struct ath_hw *ah, u32 q)
 			  AR_Q_RDYTIMECFG_EN);
 	}
 
-	REGWRITE_BUFFER_FLUSH(ah);
-
 	REG_WRITE(ah, AR_DCHNTIME(q),
 		  SM(qi->tqi_burstTime, AR_D_CHNTIME_DUR) |
 		  (qi->tqi_burstTime ? AR_D_CHNTIME_EN : 0));