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>
diff --git a/arch/Kconfig b/arch/Kconfig
index 99617b7..fdcf7cd 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -98,6 +98,7 @@
 	imply DM_ETH
 	imply DM_GPIO
 	imply DM_KEYBOARD
+	imply DM_MMC
 	imply DM_RTC
 	imply DM_SERIAL
 	imply DM_SPI