ARM: shmobile: armadillo-reference dts: Seiko Instruments, Inc is "sii"

Use "sii,s35390a" instead of "seiko,s35390a", cfr.
Documentation/devicetree/bindings/i2c/trivial-devices.txt and
Documentation/devicetree/bindings/vendor-prefixes.txt.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>