max8998_charger: Allow full timeout not set, leave it unchanged

Add a missing break for case 0 of pdata->timeout, otherwise it will fall
through to the default case and return error.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>