[scripts][python] Move a few more scripts from python2 to python3
Turns out they were already python3 safe, so just switch to requested
version over.
diff --git a/arch/arm/stackusage b/arch/arm/stackusage
index cac7ce3..d675b7e 100755
--- a/arch/arm/stackusage
+++ b/arch/arm/stackusage
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
import sys
import re
diff --git a/platform/zynq/mkbootheader.py b/platform/zynq/mkbootheader.py
index da615e9..95753cc 100755
--- a/platform/zynq/mkbootheader.py
+++ b/platform/zynq/mkbootheader.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
# generates Zynq bootrom header from input payout