Documentation/process: Add embargoed HW contact for Ampere Computing

Add Darren Hart as Ampere Computing's ambassador for the embargoed
hardware issues process.

Signed-off-by: Darren Hart <darren@os.amperecomputing.com>
Link: https://lore.kernel.org/r/2e36a8e925bc958928b4afa189b2f876c392831b.1650995848.git.darren@os.amperecomputing.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>