spl: Kconfig: Drop the _SUPPORT postfix from SPL_DFU

The symbol CONFIG_SPL_DFU_SUPPORT in SPL build has the same
meaning as CONFIG_DFU in regular U-Boot. Drop the _SUPPORT
to allow for cleaner use in code.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Lukasz Majewski <lukma@denx.de>
diff --git a/drivers/usb/gadget/Makefile b/drivers/usb/gadget/Makefile
index 01e2b3a..70f3bf4 100644
--- a/drivers/usb/gadget/Makefile
+++ b/drivers/usb/gadget/Makefile
@@ -8,7 +8,7 @@
 
 ifdef CONFIG_SPL_BUILD
 obj-$(CONFIG_SPL_USB_GADGET) += g_dnl.o
-obj-$(CONFIG_SPL_DFU_SUPPORT) += f_dfu.o
+obj-$(CONFIG_SPL_DFU) += f_dfu.o
 obj-$(CONFIG_SPL_USB_SDP_SUPPORT) += f_sdp.o
 endif