arm64: sanity checks: add ID_AA64DFR{0,1}_EL1

While we currently expect self-hosted debug support to be identical
across CPUs, we don't currently sanity check this.

This patch adds logging of the ID_AA64DFR{0,1}_EL1 values and associated
sanity checking code.

It's not clear to me whether we need to check PMUVer, TraceVer, and
DebugVer, as we don't currently rely on these fields at all.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>