Documentation: Document the Linux Kernel CVE process

The Linux kernel project now has the ability to assign CVEs to fixed
issues, so document the process and how individual developers can get a
CVE if one is not automatically assigned for their fixes.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/2024021731-essence-sadness-28fd@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>