global: Migrate CONFIG_FEC_MXC_PHYADDR to CFG

Perform a simple rename of CONFIG_FEC_MXC_PHYADDR to CFG_FEC_MXC_PHYADDR

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/doc/README.fec_mxc b/doc/README.fec_mxc
index 4e890d3..2ccd428 100644
--- a/doc/README.fec_mxc
+++ b/doc/README.fec_mxc
@@ -18,7 +18,7 @@
 CONFIG_FEC_MXC_NO_ANEG
 	Relevant only if PHYLIB not used. Skips auto-negotiation restart.
 
-CONFIG_FEC_MXC_PHYADDR
+CFG_FEC_MXC_PHYADDR
 	Optional, selects the exact phy address that should be connected
 	and function fecmxc_initialize will try to initialize it.