serial: serial_cortina: add UART DM driver for CAxxxx SoCs

Add serial UART driver support for all Cortina Access
CAxxxx family of SoCs.

Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Signed-off-by: Jason Li <jason.li@cortina-access.com>
Signed-off-by: Alex Nemirovsky <alex.nemirovsky@cortina-access.com>