mmc: sdhci-esdhc-imx: optimize the manual tuing logic to get the best timing

Current manual tuning logic only get the first pass window, but
this pass window maybe not the best pass window.

Now find all the pass window, and chose the largest pass window,
and use the average value of this largest pass window to get the
best timing.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20230831032647.3128702-1-haibo.chen@nxp.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>