8250: allow platforms to override PM hook.

Add a hook for platforms to specify custom pm methods.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index ac48082..99e5994 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -289,6 +289,8 @@
 	void			(*set_termios)(struct uart_port *,
 				               struct ktermios *new,
 				               struct ktermios *old);
+	void			(*pm)(struct uart_port *, unsigned int state,
+				      unsigned int old);
 	unsigned int		irq;			/* irq number */
 	unsigned long		irqflags;		/* irq flags  */
 	unsigned int		uartclk;		/* base uart clock */