mmc: Rename MMC_SUPPORT to MMC

Rename these options so that CONFIG_IS_ENABLED can be used with them.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
[trini: Fixup some incorrect renames]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/configs/imx6_spl.h b/include/configs/imx6_spl.h
index ede81cc..b5d5033 100644
--- a/include/configs/imx6_spl.h
+++ b/include/configs/imx6_spl.h
@@ -54,7 +54,7 @@
 #endif
 
 /* MMC support */
-#if defined(CONFIG_SPL_MMC_SUPPORT)
+#if defined(CONFIG_SPL_MMC)
 #define CONFIG_SYS_MONITOR_LEN			409600	/* 400 KB */
 #endif