global: Migrate CONFIG_POSTBOOTMENU to CFG

Perform a simple rename of CONFIG_POSTBOOTMENU to CFG_POSTBOOTMENU

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/configs/nokia_rx51.h b/include/configs/nokia_rx51.h
index 97d0868..a64b7b3 100644
--- a/include/configs/nokia_rx51.h
+++ b/include/configs/nokia_rx51.h
@@ -128,7 +128,7 @@
 	"bootmenu_delay=30\0" \
 	""
 
-#define CONFIG_POSTBOOTMENU \
+#define CFG_POSTBOOTMENU \
 	"echo;" \
 	"echo Extra commands:;" \
 	"echo run sdboot - Boot from SD card slot.;" \