mmc: core: modify scaling up/down sequence

The scaling down sequence requires the clock to be set
after selecting the corresponding bus-speed mode in the
controller.
The scaling up to HS400 requires the timing and clock to
be set to legacy.

Without the above configuration, bus-width switch fails,
further leading to CRC errors.

Change-Id: If502f28e19924264dfb99d76f6881d3167f56a05
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Pavan Anamula <pavana@codeaurora.org>