scripts: dtc-version: support git version strings too

Building dtc from git causes the version number to start with a 'v'
(e.g. v1.7.0). printf then fails to parse 'v1' as a decimal value, and
prints '000700' instead of '010700'. Subsequently, the build fails,
because '000700' is less than the required '010400' version.

Signed-off-by: Martin Hundebøll <martin@geanix.com>
diff --git a/scripts/dtc-version.sh b/scripts/dtc-version.sh
index bfb514e..53ff868 100755
--- a/scripts/dtc-version.sh
+++ b/scripts/dtc-version.sh
@@ -20,7 +20,7 @@
 	exit 1
 fi
 
-MAJOR=$($dtc -v | head -1 | awk '{print $NF}' | cut -d . -f 1)
+MAJOR=$($dtc -v | head -1 | awk '{print $NF}' | cut -d . -f 1 | tr -d v)
 MINOR=$($dtc -v | head -1 | awk '{print $NF}' | cut -d . -f 2)
 PATCH=$($dtc -v | head -1 | awk '{print $NF}' | cut -d . -f 3 | cut -d - -f 1)