cbfs: Allow CBFS to be used in SPL

Add a new Kconfig option to enable CBFS in SPL. This can be useful when
the memory-init code is in CBFS.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/fs/Makefile b/fs/Makefile
index 2ed4aea..42e669c 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -8,6 +8,7 @@
 obj-$(CONFIG_FS_LOADER) += fs.o
 obj-$(CONFIG_SPL_FS_FAT) += fat/
 obj-$(CONFIG_SPL_FS_EXT4) += ext4/
+obj-$(CONFIG_SPL_FS_CBFS) += cbfs/
 else
 obj-y				+= fs.o