mmc: show the erase group size and HC WP group size in mmcinfo output

This adds the erase group size and high-capacity WP group size to
mmcinfo's output. The erase group size is necessary to properly align
erase requests on eMMC. The high-capacity WP group size is necessary
to properly align partitions on eMMC.

Signed-off-by: Diego Santa Cruz <Diego.SantaCruz@spinetix.com>