spl: Extract legacy image handling into separate file

This patch moves the legacy image handling into a separate file, which
will be extended with other legacy image features later.

No function change intended.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Cc: Weijie Gao <weijie.gao@mediatek.com>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/common/spl/Makefile b/common/spl/Makefile
index eaa57f5..c576a78 100644
--- a/common/spl/Makefile
+++ b/common/spl/Makefile
@@ -10,6 +10,7 @@
 obj-$(CONFIG_$(SPL_TPL_)FRAMEWORK) += spl.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTROM_SUPPORT) += spl_bootrom.o
 obj-$(CONFIG_$(SPL_TPL_)LOAD_FIT) += spl_fit.o
+obj-$(CONFIG_$(SPL_TPL_)LEGACY_IMAGE_SUPPORT) += spl_legacy.o
 obj-$(CONFIG_$(SPL_TPL_)NOR_SUPPORT) += spl_nor.o
 obj-$(CONFIG_$(SPL_TPL_)XIP_SUPPORT) += spl_xip.o
 obj-$(CONFIG_$(SPL_TPL_)YMODEM_SUPPORT) += spl_ymodem.o