disk: convert CONFIG_DOS_PARTITION to Kconfig

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay73@gmail.com>
diff --git a/common/fb_mmc.c b/common/fb_mmc.c
index 81a3bd0..6c8dca2 100644
--- a/common/fb_mmc.c
+++ b/common/fb_mmc.c
@@ -133,7 +133,7 @@
 	}
 #endif
 
-#ifdef CONFIG_DOS_PARTITION
+#if CONFIG_IS_ENABLED(DOS_PARTITION)
 	if (strcmp(cmd, CONFIG_FASTBOOT_MBR_NAME) == 0) {
 		printf("%s: updating MBR\n", __func__);
 		if (is_valid_dos_buf(download_buffer)) {