spl: Rename Kconfig SPL_LEGACY_IMAGE_SUPPORT to SPL_LEGACY_IMAGE_FORMAT

This matches what this support is called in the non-SPL case. The postfix
_SUPPORT is redundant as enabling Kconfig options implies support.
With this we can use CONFIG_IS_ENABLED() as needed.

Signed-off-by: Andrew Davis <afd@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/common/spl/Makefile b/common/spl/Makefile
index e71e7be..13db3df 100644
--- a/common/spl/Makefile
+++ b/common/spl/Makefile
@@ -10,7 +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_)LEGACY_IMAGE_FORMAT) += 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