arm64: mm: decode xFSC in mem_abort_decode()

It would be helpful if mem_abort_decode() could decode the DFSC/IFSC, as
this can make it easier to identify common bugs (e.g. accesses which
trigger alignment faults) without having to manually decode the xFSC
value.

Decode the xFSC in mem_abort_decode().

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210608123742.11921-1-mark.rutland@arm.com


Signed-off-by: Will Deacon <will@kernel.org>