arm: Improve NISV reporting

An ARM NISV exit typically points either to accesses outside of known
memory locations or to the use of unsupported load/store instructions
when doing MMIO accesses.
In both cases it would be helpful to have more information to find the
root cause of this fatal exit.

Dump the fault address and the program counter to the console, to help
identifying the culprit.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>