i2c: mxs: Implement arbitrary clock speed derivation algorithm

This patch drops the i2c timing tables from this driver and instead
derives the timing based from the requested clock sleep. The timing
tables were completely wrong anyway when observed on a scope.

This new algorithm is also only derived by using a scope, but it seems
to produce much more accurate result.

Signed-off-by: Marek Vasut <marex@denx.de>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
[wsa: changed messages from dev_err to dev_warn]
Signed-off-by: Wolfram Sang <wolfram@the-dreams.de>