Revert "mmc: fsl_esdhc: fix sd/mmc ddr mode clock setting issue"

This reverts commit 72a89e0d, which
causes the imx53 HSC to hang as the eMMC is not working properly anymore.

The exact error message:
MMC write: dev # 0, block # 2, count 927 ... mmc write failed
0 blocks written: ERROR

imx53 is not using the DDR mode.

Debugging of pre_div and div generation showed that those values are
generated in a way, which is not matching the ones from working setup.

As the original patch was performing code refactoring, let's revert this
change, so all imx53 boards would work again.

Signed-off-by: Lukasz Majewski <lukma@denx.de>