arch: arm: cortex_m: fix stack overflow error detection

In rare cases when a thread may overflow its stack, the
core will not report a Stacking Error. This is the case
when a large stack array is created, making the PSP cross
beyond the stack guard; in this case a MemManage fault
won't cause a stacking error (but only a Data Access
Violation error). We fix the fault handling logic so
such errors are reported as stack overflows and not as
generic CPU exceptions.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>