Don't try to cache the page setting - always set the page before

doing a switch register read/write.

PR:		kern/172968

sys/dev/etherswitch/arswitch/arswitch_reg.c

@@ -72,11 +72,18 @@ arswitch_split_setpage(device_t dev, uint32_t addr, uint16_t *phy,
 	*phy = (((addr) >> 6) & 0x07) | 0x10;
 	*reg = ((addr) >> 1) & 0x1f;
 
-	if (sc->page != page) {
+	/*
+	 * The earlier code would only switch the page
+	 * over if the page were different.  Experiments have
+	 * shown that this is unstable.
+	 *
+	 * Hence, the page is always set here.
+	 *
+	 * See PR kern/172968
+	 */
 	MDIO_WRITEREG(device_get_parent(dev), 0x18, 0, page);
 	sc->page = page;
 }
-}
 
 /*
  * Read half a register.  Some of the registers define control bits, and