selftests: tpm: Use /bin/sh instead of /bin/bash

It's better to use /bin/sh instead of /bin/bash in order to run the tests
in the BusyBox shell.

Fixes: 6ea3dfe1 ("selftests: add TPM 2.0 tests")
Cc: stable@vger.kernel.org
Cc: linux-integrity@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/tpm2/test_smoke.sh

-#!/bin/bash
+#!/bin/sh
 # SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
 
 # Kselftest framework requirement - SKIP code is 4.

tools/testing/selftests/tpm2/test_space.sh

-#!/bin/bash
+#!/bin/sh
 # SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
 
 # Kselftest framework requirement - SKIP code is 4.