Prepare v2018.05-rc3

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/Makefile b/Makefile
index 316944c..5264df0 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@
 VERSION = 2018
 PATCHLEVEL = 05
 SUBLEVEL =
-EXTRAVERSION = -rc2
+EXTRAVERSION = -rc3
 NAME =
 
 # *DOCUMENTATION*