Revert "arm64: cpuinfo: print info for all CPUs"

It turns out that vendors are relying on the format of /proc/cpuinfo,
and we've even spotted out-of-tree hacks attempting to make it look
identical to the format used by arch/arm/. That means we can't afford to
churn this interface in mainline, so revert the recent reformatting of
the file for arm64 pending discussions on the list to find out what
people actually want.

This reverts commit d7a49086.

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