arm64: process: dump memory around registers when displaying regs

A port of 8608d7c4418c75841c562a90cddd9beae5798a48 to ARM64.  Both the
original code and this port are limited to dumping kernel addresses, so
don't bother if the registers are from a userspace process.

Change-Id: Idc76804c54efaaeb70311cbb500c54db6dac4525
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Git-commit: 081513b5f5f79f759beb2a542d89ca61c0967ac8
Git-repo: https://android.googlesource.com/kernel/common


Signed-off-by: Venkata Narendra Kumar Gutta <vnkgutta@codeaurora.org>