i2c: rcar: avoid non-standard use of goto

Kernel functions goto somewhere on error conditions. Using goto for the
default path is irritating. Let's bail out on error instead and use a
proper retval.

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>