replace shebang '/bin/bash' for '/usr/bin/env bash'

Allows better portability of bash scripting between Linux
distributions.

Change-Id: Ia0ec079581398bcffbf20bb8206860bcec0e6e7a
Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
diff --git a/run_config/fvp-spm b/run_config/fvp-spm
index 50ab24b..dc4103f 100644
--- a/run_config/fvp-spm
+++ b/run_config/fvp-spm
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # Copyright (c) 2020, Arm Limited. All rights reserved.
 #