ARM: imx: Decouple mccmon6's SPL and u-boot proper code

The mccmon6 has been used a "mixed" approach between SPL and
U-Boot proper sources.

This commit decoupes SPL and u-boot proper, which allows clear
distinction between those two code bases and facilitates
conversion to DM/DTS on this particular board.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
diff --git a/board/liebherr/mccmon6/Makefile b/board/liebherr/mccmon6/Makefile
index ead6750..3c9786c 100644
--- a/board/liebherr/mccmon6/Makefile
+++ b/board/liebherr/mccmon6/Makefile
@@ -2,5 +2,8 @@
 #
 # (C) Copyright 2016-2017
 # Lukasz Majewski, DENX Software Engineering, lukma@denx.de
-
-obj-y  := mccmon6.o spl.o
+ifdef CONFIG_SPL_BUILD
+obj-y  := spl.o
+else
+obj-y  := mccmon6.o
+endif