[U-Boot] [imx/next V2] tools: imx8m_image: use bash

[Peng Fan]

travis-ci reports
"tools/imx8m_image.sh: 15: [: signed_hdmi_imx8m.bin: unexpected operator"
After use bash, no error, so use bash instead of sh.

Signed-off-by: Peng Fan <peng.fan at nxp.com>
---
 tools/imx8m_image.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/imx8m_image.sh b/tools/imx8m_image.sh
index 6346fb64d8..0e9df4763c 100755
--- a/tools/imx8m_image.sh
+++ b/tools/imx8m_image.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # SPDX-License-Identifier: GPL-2.0+
 #
 # script to check whether the file exists in imximage.cfg for i.MX8M
-- 
2.14.1