rp2/modmachine: Enable machine.Signal class.
rp2/modmachine: Enable machine.Signal class.

Fixes issue #6863.

Signed-off-by: Damien George <99e6b749acbfbe2a596df99e91d24d6e1fdbee00@micropython.org>

pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython