x86: Convert MMC to driver model

Convert the pci_mmc driver over to driver model and migrate all x86 boards
that use it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: remove DM_MMC from edison_defconfig]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>