arch: arm: aarch32: cortex_m: fault: Fix SCB->CFSR access helpers

This is a follow-up to commit f400c94a.

Fix typos in names of introduced macros (*STR -> *SR) and cast their
values to uint32_t to avoid warnings reported for messages formatted
with %x.

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>