am43xx_evm: mmc: do not define DM_MMC for spl

Since spl doesn't support DM currently, do not define DM_MMC
for spl build.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
diff --git a/include/configs/am43xx_evm.h b/include/configs/am43xx_evm.h
index 09a3e17..d93e3e7 100644
--- a/include/configs/am43xx_evm.h
+++ b/include/configs/am43xx_evm.h
@@ -140,6 +140,14 @@
 #define CONFIG_USB_GADGET_DUALSPEED
 #endif
 
+/*
+ * Disable MMC DM for SPL build and can be re-enabled after adding
+ * DM support in SPL
+ */
+#ifdef CONFIG_SPL_BUILD
+#undef CONFIG_DM_MMC
+#endif
+
 #ifndef CONFIG_SPL_BUILD
 /* USB Device Firmware Update support */
 #define CONFIG_USB_FUNCTION_DFU