Freescale T4240QDS reference board has extra voltage shifters added
to allow 3.3V operation, so add 3.3v voltage support for T4240QDS.
1.8v and 3.3v is recommand for eMMC and SDHC card.
Signed-off-by: NHaijun Zhang <haijun.zhang@freescale.com>
Signed-off-by: NScott Wood <scottwood@freescale.com>