extcon: Rename the extcon_set/get_state() to maintain the function naming pattern
This patch just renames the existing extcon_get/set_cable_state_()
as following because of maintaining the function naming pattern
like as extcon APIs for property.
- extcon_set_cable_state_() -> extcon_set_state()
- extcon_get_cable_state_() -> extcon_get_state()
But, this patch remains the old extcon_set/get_cable_state_() functions
to prevent the build break. After altering new APIs, remove the old APIs.