HardFault regression detected on Cortex-M0+ following Cortex-R introduction

[ABOSTM]

Describe the bug
A bunch of tests are now reported failed on Cortex-M0+ based board (nucleo_g071rb, nucleo_l073rz).
Regression occurs since merge of Cortex-R PR: #28231

To Reproduce
Steps to reproduce the behavior:

1. west build -p auto -b nucleo_g071rb tests/kernel/mutex/mutex_api/
2. west flash
3. See error

Logs and console output

*** Booting Zephyr OS build zephyr-v2.6.0-2072-gb055054d417b  ***
Running test suite mutex_api
===================================================================
START - test_mutex_lock_unlock
E: ***** HARD FAULT *****

Environment (please complete the following information):

• OS: both. Linux and Windows
• Toolchain Zephyr SDK
• Commit SHA : 4ffb90f202f832c7a6f1eca0fedb030354583946d

[ABOSTM]

Analysis
Regression has been introduced in arch\arm\core\aarch32\userspace.S
by e0bed3b "arch: arm: cortex_r: Add MPU and USERSPACE support"
(PR #28231)

It introuced unintended ASM instruction " msr PSP, ip" for CONFIG_ARMV6_M_ARMV8_M_BASELINE:
code :

#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
    /* set stack back to unprivileged stack */
    mov ip, r0
    mov r0, sp
    ldr r0, [r0,#12]
    msr PSP, r0
    /* Restore r0 */
    mov r0, ip

#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE) \
    || defined(CONFIG_CPU_CORTEX_R)
    /* set stack back to unprivileged stack */
    ldr ip, [sp,#12]
#endif

#if defined(CONFIG_CPU_CORTEX_R)
    mov sp, ip
#else
    msr PSP, ip
#endif

as been replaced by

#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
    /* set stack back to unprivileged stack */
    mov ip, r0
    mov r0, sp
    ldr r0, [r0,#12]
    msr PSP, r0
    /* Restore r0 */
    mov r0, ip

#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE) \
    || defined(CONFIG_CPU_CORTEX_R)
    /* set stack back to unprivileged stack */
    ldr ip, [sp,#12]
#endif

#if defined(CONFIG_CPU_CORTEX_R)
    mov sp, ip
#else
    msr PSP, ip
#endif

Thus "msr PSP, ip" is present to all arch expect cortex-R whereas it was initially not present for ARMV6_M_ARMV8_M_BASELINE