serial: sccnxp: Replace pdata.init/exit with regulator API

Typical usage of pdata.init/exit is enable/disable power and/or toggle
reset for the target chip.
This patch replaces these callbacks with regulator API.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>