mmc: atmel-mci: enable SD high speed support

Enable high speed support for atmel-mci driver.  This support is dependent
of the revision of the IP and, of course, the capacity of the SD card
used.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Reviewed-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Cc: Maciej Sosnowski <maciej.sosnowski@intel.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>