[SERIAL] Make uart_port flags a bitwise type

Same reasoning as commit 747c8a5594
but this time we're making uart_port flags a bitwise type - not
all of these flags correspond with the old ASYNC_ flags, so there
is the possibility for bugs if the wrong ASYNC_* constants are
used.  Always use UPF_* constants for uart_port->flags.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

include/linux/serial_8250.h

@@ -26,7 +26,7 @@ struct plat_serial8250_port {
 	unsigned char	regshift;	/* register shift */
 	unsigned char	iotype;		/* UPIO_* */
 	unsigned char	hub6;
-	unsigned int	flags;		/* UPF_* flags */
+	upf_t		flags;		/* UPF_* flags */
 };
 
 /*