python3-cryptography: convert to cargo-update-recipe-crates class

This allows semi-automated updates to the list of crates, which
is far too awkward to maintain by hand, particularly on version updates.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>