rtc-m48t59: allow externally mapped ioaddr

Add support for externally mapped ioaddr.  This is required on sparc32
as the ioaddr must be mapped with of_ioremap().

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/rtc/m48t59.h

@@ -55,6 +55,8 @@ struct m48t59_plat_data {
 
 	int type; /* RTC model */
 
+	/* ioaddr mapped externally */
+	void __iomem *ioaddr;
 	/* offset to RTC registers, automatically set according to the type */
 	unsigned int offset;
 };