ARM: dts: r8a7740: Add CEU1

Describe CEU1 peripheral for Renesas R-Mobile A1 R8A7740 Soc.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>