Makefile: move fs/fat/ entry to drivers/Makefile

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/fs/Makefile b/fs/Makefile
index bdcd746..ee01a7d 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -6,11 +6,15 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
+ifdef CONFIG_SPL_BUILD
+obj-$(CONFIG_SPL_FAT_SUPPORT) += fat/
+else
 obj-y				+= fs.o
 
 obj-y += cbfs/
 obj-y += cramfs/
 obj-y += ext4/
+obj-y += fat/
 obj-y += fdos/
 obj-y += jffs2/
 obj-y += reiserfs/
@@ -18,3 +22,4 @@
 obj-y += ubifs/
 obj-y += yaffs2/
 obj-y += zfs/
+endif