Documentation: embargoed-hardware-issues.rst: add AMD to the list

Add AMD back to the embargoed-hardware-issues.rst list.  There was
confusion about a recent issue that ended up being due to third-party's
misrepresentation, not AMD, so add AMD back to the list to get notified
properly as they understand the proper procedures to follow.

Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/2023072514-submersed-yanking-652e@gregkh


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>