i2c: rcar: clean up after refactoring i2c_timings

The pointer is not really needed anymore since we have the timings
struct available in the function itself now. Remove the pointer and
access the struct directly.

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