i2c: rcar: cleanup DMA for all kinds of failure

DMA needs to be cleaned up not only on timeout, but on all errors where
it has been setup before.

Fixes: 73e8b052

 ("i2c: rcar: add DMA support")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>