net: sfp: provide a definition for the power level select bit

Provide a named definition for the power level select bit in the
extended status register, rather than using BIT(0) in the code.
Signed-off-by: NRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

drivers/net/phy/sfp.c

@@ -1837,13 +1837,13 @@ static int sfp_sm_mod_hpower(struct sfp *sfp, bool enable)
 	 * all bytes 0xff) at 0x51 but does not accept writes.  In any case,
 	 * if the bit is already set, we're already in high power mode.
 	 */
-	if (!!(val & BIT(0)) == enable)
+	if (!!(val & SFP_EXT_STATUS_PWRLVL_SELECT) == enable)
 		return 0;
 
 	if (enable)
-		val |= BIT(0);
+		val |= SFP_EXT_STATUS_PWRLVL_SELECT;
 	else
-		val &= ~BIT(0);
+		val &= ~SFP_EXT_STATUS_PWRLVL_SELECT;
 
 	err = sfp_write(sfp, true, SFP_EXT_STATUS, &val, sizeof(val));
 	if (err != sizeof(val)) {

include/linux/sfp.h

@@ -489,6 +489,8 @@ enum {
 	SFP_WARN1_RXPWR_LOW		= BIT(6),
 
 	SFP_EXT_STATUS			= 0x76,
+	SFP_EXT_STATUS_PWRLVL_SELECT	= BIT(0),
+
 	SFP_VSL				= 0x78,
 	SFP_PAGE			= 0x7f,
 };