mmc: MMC-4.5 Data Tag Support

MMC-4.5 data tag feature will be used to store the file system meta-data
in the tagged region of eMMC. This will improve the write and subsequent
read transfer time for the meta data.

Signed-off-by: Saugata Das <saugata.das@linaro.org>
Tested-by: Venkatraman S <svenkatr@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>