i2c: xiic: Improve struct memory alignment

xiic_i2c struct alignment causes the struct to
take more space in memory than strictly required.
Move state -member to end of struct to get less
padding.

Signed-off-by: Jaakko Laine <ext-jaakko.laine@vaisala.com>
Suggested-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>