mmc: add no simultaenous power and vdd

Bring in the code from Linux kernel.

Added to Linux kernel by:
commit e08c1694d9e2138204f2b79b73f0f159074ce2f5
Author: Andres Salomon <dilinger@queued.net>
Date:   Fri Jul 4 10:00:03 2008 -0700

Some HW balks when writing both voltage setting and power up at the same
time to SDHCI_POWER_CONTROL register.

Signed-off-by: Rommel G Custodio <sessyargc@gmail.com>
CC: Andy Fleming <afleming@freescale.com>

v2: fix attribution and SOB
Signed-off-by: Andy Fleming <afleming@freescale.com>