tests/kernel/mem_protect/syscalls failed on iotdk board.

[chen-png]

To Reproduce
Steps to reproduce the behavior:

1. west build -b iotdk -p auto tests/kernel/mem_protect/syscalls
2. west flash
3. See error

Screenshots or console output
*** Booting Zephyr OS build zephyr-v2.2.0-375-ge13205b25657 ***
Running test suite syscalls

starting test - test_string_nlen
PASS - test_string_nlen

starting test - test_string_nlen
E: syscall z_vrfy_string_nlen failed check: Memory region 0x80000ff4 (size 24) read access denied
PASS - test_string_nlen

starting test - test_to_copy
E: syscall user_copy failed check: Memory region 0x80000fd4 (size 32) write access denied
PASS - test_to_copy

starting test - test_user_string_copy
E: string too long 0x2000bebc (32)
E: syscall user_copy failed check: Memory region 0x80000ff4 (size 24) read access denied
PASS - test_user_string_copy

starting test - test_user_string_alloc_copy
E: string too long 0x2000bebc (32)
E: syscall z_user_alloc_from_copy failed check: Memory region 0x80000ff4 (size 24) read access denied
PASS - test_user_string_alloc_copy

starting test - test_arg64
PASS - test_arg64

starting test - test_syscall_torture
Running syscall torture test with 4 threads on 1 cpu(s)
E: ***** Exception vector: 0x6, cause code: 0x2, parameter 0x2
E: Address 0x80004fb8
E: >>> ZEPHYR FATAL ERROR 2: Stack overflow on CPU 0
E: Current thread: 0x80000bec (unknown)
E: Halting system

Environment (please complete the following information):

• OS: fedora 28
• Toolchain : zephyr-sdk-0.11.1
• Commit ID: e13205b

[vonhust]

Fixed by #24284