kbuild: .gitignore utsrelease.h

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

.gitignore

@@ -30,6 +30,7 @@ include/config
 include/linux/autoconf.h
 include/linux/compile.h
 include/linux/version.h
+include/linux/utsrelease.h
 
 # stgit generated dirs
 patches-*