Makefile: add EXTRAVERSION for linux4sam 5.0-beta1

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

Author: Nicolas Ferre

Makefile

@@ -1,7 +1,7 @@
 VERSION = 4
 PATCHLEVEL = 1
 SUBLEVEL = 0
-EXTRAVERSION =
+EXTRAVERSION = -linux4sam_5.0-beta1
 NAME = Hurr durr I'ma sheep
 
 # *DOCUMENTATION*