extcon-max8997: remove usage of ret in max8997_muic_handle_charger_type_detach

actually we can do returns with error or success with out ret in this function,
so remove the ret variable, and reduce a very little (4byte) space on stack of this function

Signed-off-by: Devendra Naga <develkernel412222@gmail.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>