Prepare v2018.05-rc2

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/Makefile b/Makefile
index 5cfe43f..64351eb 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@
 VERSION = 2018
 PATCHLEVEL = 05
 SUBLEVEL =
-EXTRAVERSION = -rc1
+EXTRAVERSION = -rc2
 NAME =
 
 # *DOCUMENTATION*