mmc: sdhci: highspeed: check for mmc as well as sd cards

The SD and MMC code set highspeed using different constants.
Change the sd driver to recognize this and switch to high speed.
Validated code when testing eMMC dual data rate.

Signed-off-by: Philip Rakity <prakity@marvell.com>
[cjb: changelog + indentation fixes]
Signed-off-by: Chris Ball <cjb@laptop.org>