base-files: support booting from partitioned device-mapper device

package/base-files/files/lib/functions/iopsys-system-layout.sh

@@ -258,6 +258,8 @@ get_real_root_device() {
     local real_root_dev=$(get_kernel_cmdline_param root)
     # need to dig deeper in case of device mapper
     case "$real_root_dev" in
+    /dev/dm-[0-9]*p[0-9]*)
+        ;;
     /dev/dm-*)
         real_root_dev=$(get_dm_underlying_device "$real_root_dev")
         ;;
@@ -277,7 +279,7 @@ get_root_device_type() {
         local root_dev="$(get_real_root_device)"
     fi
     case "$root_dev" in
-    /dev/mmcblk* | /dev/flash-rootfs*)
+    /dev/mmcblk* | /dev/flash-rootfs* | /dev/dm-[0-9]*p[0-9]* )
         echo emmc
         ;;
     /dev/ubiblock* | ubi*:*)