mmc: tangier: Add Intel Tangier eMMC/SDHCI driver

mmc: tangier: Add Intel Tangier eMMC/SDHCI driver

This patch adds Intel Tangier eMMC/SDHCI driver.

Intel Tangier SoC contains a hybrid of PCI and non-PCI devices. SDHCI
controller is one of the devices which are *not* on a PCI and, hence,
cannot be enumerated by standard PCI means. This driver, allows for
SDHCI controller on Tangier SoC to work in U-Boot.

Signed-off-by: Vincent Tinelli <vincent.tinelli@intel.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>