[ARM] 5543/1: arm: serial amba: add missing declaration in serial.h

This header is sometimes included in the uncompress stage to get
register values, but no <linux/amba/bus.h> can be included there.
So declare "struct amba_device" here before using it in a prototype.
Signed-off-by: Alessandro Rubini <rubini@unipv.it>
Acked-by: Andrea Gallo <andrea.gallo@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

include/linux/amba/serial.h

@@ -159,6 +159,7 @@
 #define UART01x_FR_MODEM_ANY	(UART01x_FR_DCD|UART01x_FR_DSR|UART01x_FR_CTS)
 
 #ifndef __ASSEMBLY__
+struct amba_device; /* in uncompress this is included but amba/bus.h is not */
 struct amba_pl010_data {
 	void (*set_mctrl)(struct amba_device *dev, void __iomem *base, unsigned int mctrl);
 };