mmc: meson: add MMC driver for Meson GX (S905)

This driver implements MMC support on Meson GX (S905) based systems.
It's based on Carlo Caione's work, changes:
- BLK support added
- general refactoring

Signed-off-by: Carlo Caione <carlo@caione.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Tested-by: Vagrant Cascadian <vagrant@debian.org>
diff --git a/drivers/mmc/Kconfig b/drivers/mmc/Kconfig
index 560391f..077b184 100644
--- a/drivers/mmc/Kconfig
+++ b/drivers/mmc/Kconfig
@@ -105,6 +105,12 @@
 	  Synopsys DesignWare Memory Card Interface driver. Select this option
 	  for platforms based on Altera SOCFPGA.
 
+config MMC_MESON_GX
+	bool "Meson GX EMMC controller support"
+	depends on DM_MMC && BLK && DM_MMC_OPS && ARCH_MESON
+	help
+	 Support for EMMC host controller on Meson GX ARM SoCs platform (S905)
+
 config MMC_MXC
 	bool "Freescale i.MX21/27/31 or MPC512x Multimedia Card support"
 	help