serial: cpm_uart: use container_of to resolve uart_cpm_port from uart_port

Use container_of instead of casting first structure member.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --cc drivers/tty/serial/cpm_uart/cpm_uart_core.c
Simple merge