Prepare v2021.07-rc4

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/Makefile b/Makefile
index e048113..a73481d 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@
 VERSION = 2021
 PATCHLEVEL = 07
 SUBLEVEL =
-EXTRAVERSION = -rc3
+EXTRAVERSION = -rc4
 NAME =
 
 # *DOCUMENTATION*