iwlwifi: refactor rx register initialization

The patch adds HW bug W/A FH_RCSR_CHNL0_RX_IGNORE_RXF_EMPTY so that we
can enable again interrupt coalescing. It also uses named constants for
open code.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-fh.h b/drivers/net/wireless/iwlwifi/iwl-fh.h
index cd11c0c..a72efdf 100644
--- a/drivers/net/wireless/iwlwifi/iwl-fh.h
+++ b/drivers/net/wireless/iwlwifi/iwl-fh.h
@@ -247,8 +247,8 @@
 #define FH_RCSR_CHNL0_RX_CONFIG_RBDBC_SIZE_MSK (0x00F00000) /* bits 20-23 */
 #define FH_RCSR_CHNL0_RX_CONFIG_DMA_CHNL_EN_MSK (0xC0000000) /* bits 30-31*/
 
-#define FH_RCSR_RX_CONFIG_RBDCB_SIZE_BITSHIFT	(20)
-#define FH_RCSR_RX_CONFIG_REG_IRQ_RBTH_BITSHIFT	(4)
+#define FH_RCSR_RX_CONFIG_RBDCB_SIZE_POS	(20)
+#define FH_RCSR_RX_CONFIG_REG_IRQ_RBTH_POS	(4)
 #define RX_RB_TIMEOUT	(0x10)
 
 #define FH_RCSR_RX_CONFIG_CHNL_EN_PAUSE_VAL         (0x00000000)
@@ -260,8 +260,9 @@
 #define FH_RCSR_RX_CONFIG_REG_VAL_RB_SIZE_12K   (0x00020000)
 #define FH_RCSR_RX_CONFIG_REG_VAL_RB_SIZE_16K   (0x00030000)
 
-#define FH_RCSR_CHNL0_RX_CONFIG_IRQ_DEST_NO_INT_VAL       (0x00000000)
-#define FH_RCSR_CHNL0_RX_CONFIG_IRQ_DEST_INT_HOST_VAL     (0x00001000)
+#define FH_RCSR_CHNL0_RX_IGNORE_RXF_EMPTY              (0x00000004)
+#define FH_RCSR_CHNL0_RX_CONFIG_IRQ_DEST_NO_INT_VAL    (0x00000000)
+#define FH_RCSR_CHNL0_RX_CONFIG_IRQ_DEST_INT_HOST_VAL  (0x00001000)
 
 
 /**