cpm_uart: Add generic clock API support to set baudrates

This patch introduces baudrate setting support via the generic clock API.
When present the optional device tree clock property is used instead of
fsl-cpm-brg. Platforms can then define complex clock schemes, to output
the serial clock on an external pin for instance.

Signed-off-by: Laurent Pinchart <laurentp@cse-semaphore.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

drivers/serial/cpm_uart/cpm_uart.h

@@ -77,6 +77,7 @@ struct uart_cpm_port {
 	unsigned char		*rx_buf;
 	u32			flags;
 	void			(*set_lineif)(struct uart_cpm_port *);
+	struct clk		*clk;
 	u8			brg;
 	uint			 dp_addr;
 	void			*mem_addr;