extcon: Remove deprecated extcon_set/get_cable_state_()

The commit 575c2b86 ("extcon: Rename the extcon_set/get_state()
to maintain the function naming pattern") renames the extcon function as
following: But, the extcon just keeps the old API to prevent the build error.
This patch removes the deprecatd extcon API.

- extcon_get_cable_state_() -> extcon_get_state()
- extcon_set_cable_state_() -> extcon_set_state_sync()

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>