rtc: msc313: fix missing include

The driver needs io.h
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210927063724.312687-1-alexandre.belloni@bootlin.com

drivers/rtc/rtc-msc313.c

@@ -10,6 +10,7 @@
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/io.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/platform_device.h>