When hardware doesn't support High Speed Mode, we forget bus_freq_hz
timing adjustment. This makes the timings and real registers being
unsynchronized. Adjust bus_freq_hz when refuse high speed mode set.

Fixes: b6e67145 ("i2c: designware: Enable high speed mode")
Reported-by: "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>