perf: arm64: Record the user-mode PC in the call chain.

With this change, we no longer lose the innermost entry in the user-mode
part of the call chain.  See also the x86 port, which includes the ip,
and the corresponding change in arch/arm.

Signed-off-by: Jed Davis <jld@mozilla.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>