extcon: max8997: Fix return value

Return the value obtained from the function instead of hardcoding.
Fixes the following warnings:
drivers/extcon/extcon-max8997.c:235 max8997_muic_set_path() info:
why not propagate 'ret' from max8997_update_reg() instead of (-11)?
drivers/extcon/extcon-max8997.c:248 max8997_muic_set_path() info:
why not propagate 'ret' from max8997_update_reg() instead of (-11)?

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Myungjoo Ham <myungjoo.ham@samsung.com>