Revert "mmc: core: Refactor bus speed selection code"

This reverts commit dfcf52114f38a8180e04d0bb6852e89d0f36e411.

Change-Id: I9731532977558afeccdf7a9b98774c15c6bfeeb1
Merge "Revert "mmc: core: Refactor bus speed selection code"" into kk_2.7-stable