dsa: mv88e6xxx: hide unused functions

When CONFIG_NET_DSA_HWMON is disabled, we get warnings about two unused
functions whose only callers are all inside of an #ifdef:

drivers/net/dsa/mv88e6xxx.c:3257:12: 'mv88e6xxx_mdio_page_write' defined but not used [-Werror=unused-function]
drivers/net/dsa/mv88e6xxx.c:3244:12: 'mv88e6xxx_mdio_page_read' defined but not used [-Werror=unused-function]

This adds another ifdef around the function definitions. The warnings
appeared after the functions were marked 'static', but the problem
was already there before that.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 57d3231057e9 ("net: dsa: mv88e6xxx: fix style issues")
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -3187,6 +3187,7 @@ static int mv88e6xxx_set_addr(struct dsa_switch *ds, u8 *addr)
 	return err;
 }
 
+#ifdef CONFIG_NET_DSA_HWMON
 static int mv88e6xxx_mdio_page_read(struct dsa_switch *ds, int port, int page,
 				    int reg)
 {
@@ -3212,6 +3213,7 @@ static int mv88e6xxx_mdio_page_write(struct dsa_switch *ds, int port, int page,
 
 	return ret;
 }
+#endif
 
 static int mv88e6xxx_port_to_mdio_addr(struct mv88e6xxx_chip *chip, int port)
 {