ARC: unable to induce kernel_oops or stack check fail errors from user mode

[andrewboie]

Steps to reproduce:

Pull #17589
And run tests/kernel/mem_protect/userspace
All cases need to succeed.
Right now, calling z_arch_except() from user mode results in an EV_PrivilegeV error.
The result is that the wrong error reason is reported.

[vonhust]

Fixed by PR #18079