global: Migrate CONFIG_SH_ETHER_USE_PORT to CFG

Perform a simple rename of CONFIG_SH_ETHER_USE_PORT to CFG_SH_ETHER_USE_PORT

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/README b/README
index 217fbaf..a9b225e 100644
--- a/README
+++ b/README
@@ -541,7 +541,7 @@
 		CONFIG_SH_ETHER
 		Support for Renesas on-chip Ethernet controller
 
-			CONFIG_SH_ETHER_USE_PORT
+			CFG_SH_ETHER_USE_PORT
 			Define the number of ports to be used
 
 			CFG_SH_ETHER_PHY_ADDR