According the JEDEC specification an eMMC card supporting 1.8V vccq in DDR
mode should also be capable of 3.3V. However, it's been reported that some
mmc hosts supports 3.3V, but not 1.8V.

Currently the mmc core implements an error handling when the host fails to
set 1.8V for vccq, by falling back to 3.3V. Unfortunate, this seems to be
insufficient for some mmc hosts. To enable these to use eMMC DDR mode let's
invent a new mmc cap, MMC_CAP_3_3V_DDR, which tells whether they support
the eMMC 3.3V DDR mode.

In case MMC_CAP_3_3V_DDR is set, but not MMC_CAP_1_8V_DDR, let's change to
remain on the 3.3V, as it's the default voltage level for vccq, set by the
earlier power up sequence.

As this change introduces MMC_CAP_3_3V_DDR, let's take the opportunity to
do some re-formatting of the related defines in the header file.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Tested-by: Jan Glauber <jglauber@cavium.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>