mmc: Add mmc_dev()

This macro is necessary for arasan_zynqmp_dll_reset to compile.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/include/mmc.h b/include/mmc.h
index 8256219..75bcaaf 100644
--- a/include/mmc.h
+++ b/include/mmc.h
@@ -888,6 +888,8 @@
 #define mmc_host_is_spi(mmc)	0
 #endif
 
+#define mmc_dev(x)	((x)->dev)
+
 void board_mmc_power_init(void);
 int board_mmc_init(struct bd_info *bis);
 int cpu_mmc_init(struct bd_info *bis);