arch: arm: force MpuFaultHandler to inspect multiple error conditions

Upon MemManage Exception, multiple status bits of MMFSR may be
set. This commit modifies the MPU Fault Handler, so that it can
inspect and display information from all error conditions,
instead of just the first error condition that is true.

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