tests: error_hook: Fix trigger_fault_access for Cortex-R

The Cortex-R platforms may no use XIP which means userspace code with
have read and execute access to some of the RAM so that it can execute
code.  However, userspace will not have access the the protected
read/write parts of RAM so it is safe to use the Cortex-M version of
trigger_fault_access for this test.

Signed-off-by: Bradley Bolen <bbolen@lexmark.com>