mmc: sdhci: Turn on controller clocks and card power at MMC_POWER_UP

Currently, the clock to the card is enabled prior to enabling
the power to card. Specification requires that the power be
supplied first and then a delay of 10ms and then clock be
provided to the card.

In this, during MMC_POWER_UP mode, the controller clocks would be
ON and the power would be supplied to the card. In the MMC_POWER_ON
mode, the clocks to the card would be enabled and the rate set.
A callback has been provided to facilitate the enabling of
controller clocks.

CRs-Fixed: 567658
Change-Id: I2d66eae1581b9b136faaba4cafc330aeb6a3f364
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>