scripts/getver.sh: simplify revision calculation

Use git rev-list --count to get the revision number.

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>

scripts/getver.sh

@@ -11,7 +11,7 @@ try_version() {
 
 try_git() {
 	git rev-parse --git-dir >/dev/null 2>&1 || return 1
-	REV="$(git describe --match reboot | sed "s/reboot-\([0-9]*\)-.*/\1/g")"
+	REV="$(git rev-list reboot..HEAD --count)"
 	REV="${REV:+r$REV}"
 	[ -n "$REV" ]
 }