mmc: atmel_sdhci: Convert to the driver model support

Convert the driver to the driver model while retaining the existing
legacy code. This allows the driver to support boards that have
converted to driver model as well as those that have not.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
diff --git a/drivers/mmc/Kconfig b/drivers/mmc/Kconfig
index dc8f2b6..3616dee 100644
--- a/drivers/mmc/Kconfig
+++ b/drivers/mmc/Kconfig
@@ -34,6 +34,16 @@
           SD 3.0 specifications. Both SD and eMMC devices are supported.
 	  Card-detect gpios are not supported.
 
+config ATMEL_SDHCI
+	bool "Atmel SDHCI controller support"
+	depends on DM_MMC && BLK && DM_MMC_OPS && ARCH_AT91
+	help
+	  This enables support for the Atmel SDHCI controller, which supports
+	  the embedded MultiMedia Card (e.MMC) Specification V4.51, the SD
+	  Memory Card Specification V3.0, and the SDIO V3.0 specification.
+	  It is compliant with the SD Host Controller Standard V3.0
+	  specification.
+
 config ROCKCHIP_DWMMC
 	bool "Rockchip SD/MMC controller support"
 	depends on DM_MMC && OF_CONTROL