Merge tag 'mmc-2019-7-15' of https://gitlab.denx.de/u-boot/custodians/u-boot-mmc

- mmc spi driver model support
- drop mmc_spi command
- enhanced Strobe mmc HS400 support
- minor mmc bug/fixes and optimization
- omap hsmmc and mvbeu update
- sdhci card detect support