mfd: wm8350 tries reaches -1

With a postfix decrement tries will reach -1 rather than 0,
so the warning will not be issued even upon timeout.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@openedhand.com>