UPSTREAM: arm64: decode ESR_ELx.EC when reporting exceptions

To aid the developer when something triggers an unexpected exception,
decode the ESR_ELx.EC field when logging an ESR_ELx value. This doesn't
tell the developer the specifics of the exception encoded in the
remaining IL and ISS bits, but it can be helpful to distinguish between
exception classes (e.g. SError and a data abort) without having to
manually decode the field, which can be tiresome.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>

Bug: 31432001
Change-Id: I0e87cbc3724fc3b89ad4251a4a4b4550a67977a3
(cherry picked from commit 60a1f02c9e91e0796b54e83b14fb8a07f7a568b6)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>