ath9k_hw: Disable PAPRD for rates with low Tx power

When the drop in Tx power for a particular mcs rate exceeds
the paprd scale factor, paprd may not work properly. Disable
paprd for any such rates.

Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/hw.h b/drivers/net/wireless/ath/ath9k/hw.h
index fb64ab8..3a6101b 100644
--- a/drivers/net/wireless/ath/ath9k/hw.h
+++ b/drivers/net/wireless/ath/ath9k/hw.h
@@ -835,6 +835,7 @@
 
 	unsigned int paprd_target_power;
 	unsigned int paprd_training_power;
+	unsigned int paprd_ratemask;
 	u32 paprd_gain_table_entries[PAPRD_GAIN_TABLE_ENTRIES];
 	u8 paprd_gain_table_index[PAPRD_GAIN_TABLE_ENTRIES];
 	/*