sh_eth: add/use RMCR.RNC bit

Declare 'enum RMCR_BIT' containing the single member for the RMCR.RNC bit and
replace bare numbers in the driver by this mnemonic.

Suggested-by: David Miller <[e-mail]>
Signed-off-by: Sergei Shtylyov <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/renesas/sh_eth.c

···
 	.register_type	= SH_ETH_REG_FAST_SH4,
 
 	.eesipr_value	= DMAC_M_RFRMER | DMAC_M_ECI | 0x003fffff,
-	.rmcr_value	= 0x00000001,
+	.rmcr_value	= RMCR_RNC,
 
 	.tx_check	= EESR_FTC | EESR_CND | EESR_DLC | EESR_CD | EESR_RTO,
 	.eesr_err_check	= EESR_TWB | EESR_TABT | EESR_RABT | EESR_RFE |
···
 			  EESR_RFE | EESR_RDE | EESR_RFRMER | EESR_TFE |
 			  EESR_TDE | EESR_ECI,
 	.fdr_value	= 0x0000072f,
-	.rmcr_value	= 0x00000001,
+	.rmcr_value	= RMCR_RNC,
 
 	.irq_flags	= IRQF_SHARED,
 	.apr		= 1,
···
 			  EESR_RFE | EESR_RDE | EESR_RFRMER | EESR_TFE |
 			  EESR_TDE | EESR_ECI,
 	.fdr_value	= 0x0000070f,
-	.rmcr_value	= 0x00000001,
+	.rmcr_value	= RMCR_RNC,
 
 	.apr		= 1,
 	.mpr		= 1,

drivers/net/ethernet/renesas/sh_eth.h

···
 #define TD_TFP	(TD_TFP1|TD_TFP0)
 
 /* RMCR */
+enum RMCR_BIT {
+	RMCR_RNC = 0x00000001,
+};
 #define DEFAULT_RMCR_VALUE	0x00000000
 
 /* ECMR */