media: dt-bindings: media: renesas-ceu: Add R-Mobile R8A7740

Add R-Mobile A1 R8A7740 SoC to the list of compatible values for the CEU
unit.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>