Prepare v2018.03-rc4

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/Makefile b/Makefile
index 50abc97..c6819d5 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@
 VERSION = 2018
 PATCHLEVEL = 03
 SUBLEVEL =
-EXTRAVERSION = -rc3
+EXTRAVERSION = -rc4
 NAME =
 
 # *DOCUMENTATION*