arm: add CPU_CORTEX_M_HAS_PROGRAMMABLE_FAULT_PRIOS kconfig flag

Cortex-M0/M0+ do not have other faults than the hard fault at priority
-1, so they do not need to reserve a priority to allow exceptions to
trigger during handling of ISRs.

Change-Id: I479e439f7bcac70b4b2b787bcd744a4c65437e80
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
1 file changed