i2c: rcar: Drop "renesas,i2c-rcar"

The compatible value "renesas,i2c-rcar" was deprecated in commit
ad4a8dc3 ("i2c: rcar: Add per-Generation fallback bindings"),
and never had any users in upstream Linux.  Drop its match entry from
the driver.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@kernel.org>