i2c: rcar: reset controller is mandatory for Gen3+

i2c: rcar: reset controller is mandatory for Gen3+

Initially, we only needed a reset controller to make sure RXDMA works at
least once per transfer. Meanwhile, documentation has been updated. It
now says that a reset has to be performed prior every transaction, even
if it is non-DMA. So, make the reset controller a requirement instead of
being optional. And bail out if resetting fails.

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