arm: mvebu: fix vendor prefix typo in kirkwood-synology.dtsi

As reported by Andrew, the vendor prefix for Seiko Instruments, Inc.
S-35390A I2C RTC chip in kirkwood-synology.dtsi has a typo (ssi
instead of sii). This patches fixes it.

Note: i2c devices ignore the optional vendor prefix, which explains
why it worked with the typo and also why there is no backward
compatibility issues with the fix.
Reported-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Link: https://lkml.kernel.org/r/0444140a267d982c3e5f5f2b7b5f2dc41d010e2a.1416613429.git.arno@natisbad.orgSigned-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/boot/dts/kirkwood-synology.dtsi

@@ -266,7 +266,7 @@ rs5c372: rs5c372@32 {
 
 			s35390a: s35390a@30 {
 				status = "disabled";
-				compatible = "ssi,s35390a";
+				compatible = "sii,s35390a";
 				reg = <0x30>;
 			};
 		};