selftests/mm: switch to bash from sh

Running charge_reserved_hugetlb.sh generates errors if sh is set to
dash:

./charge_reserved_hugetlb.sh: 9: [[: not found
./charge_reserved_hugetlb.sh: 19: [[: not found
./charge_reserved_hugetlb.sh: 27: [[: not found
./charge_reserved_hugetlb.sh: 37: [[: not found
./charge_reserved_hugetlb.sh: 45: Syntax error: "(" unexpected

Switch to using /bin/bash instead of /bin/sh.  Make the switch for
write_hugetlb_memory.sh as well which is called from
charge_reserved_hugetlb.sh.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Muhammad Usama Anjum <[email protected]>
Cc: Muhammad Usama Anjum <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: David Laight <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: musamaanjum

tools/testing/selftests/mm/charge_reserved_hugetlb.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
 # Kselftest framework requirement - SKIP code is 4.

tools/testing/selftests/mm/write_hugetlb_memory.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
 set -e