Documentation: embargoed-hardware-issues.rst: Clarify prenotifaction

Documentation: embargoed-hardware-issues.rst: Clarify prenotifaction

There has been a repeated misunderstanding about what the hardware embargo
list is for. Clarify the language in the process so that it is clear
that only fixes are coordinated. There is explicitly no prenotification
process. The list members are also expected to keep total radio silence
during embargoes.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: workflows@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231004004959.work.258-kees@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>