i2c: rcar: Prepare for the advent of ARCH_RCAR_GEN4

Currently, all Kconfig symbols for R-Car Gen4 SoCs select
ARCH_RCAR_GEN3, which might confuse the casual reader.  Prepare for the
advent of ARCH_RCAR_GEN4 by extending the dependency for auto-selecting
reset controller support.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>