extmod/moduselect: Fix unsigned/signed comparison for timeout!=-1.
extmod/moduselect: Fix unsigned/signed comparison for timeout!=-1.

Signed-off-by: Jim Mussared <e84f5c941266186d0c97dcc873413469b954847e@gmail.com>

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