Revert "serial: mctrl_gpio: split disable_ms into sync and no_sync APIs"

This reverts commit 68435c1f which is
commit 1bd2aad5 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I5a1f6ecb6b0139b48d9cbfeff2efde4362d6f3b0
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>