drivers: serial: Initial support for Renesas RX serial driver

Intial serial driver support for RX MCU, this driver utilize
the SCI HWIP for uart communication
Current support include polling API and Interrupt driven API,
some of the code is using Renesas RX Driver Package (RDP) as
hal layer

Signed-off-by: Duy Nguyen <duy.nguyen.xa@renesas.com>
Signed-off-by: Sang Tran <sang.tran.jc@renesas.com>