MMC SDHCI maintainer Adrian Hunter Introduce SDHCI flags for signal voltage support and set them based on the supported transfer modes, except in the case where 3V DDR52 is supported but 1.8V is not. This patch add the support to make eMMC DDR52 only work at 3.3v when property 'no-1-8-v' defined. Signed-off-by: Haibo Chen <haibo.chen@nxp.com>