ColdFire: Add $(obj) before cpu lib to correct build

Missing $(obj) prevented the build of ColdFire boards in a directory
than sources

Signed-off-by: Stany MARCEL <stany.marcel@novasys-ingenierie.com>
diff --git a/arch/m68k/cpu/mcf5445x/Makefile b/arch/m68k/cpu/mcf5445x/Makefile
index 047e35d..5b7ddd6 100644
--- a/arch/m68k/cpu/mcf5445x/Makefile
+++ b/arch/m68k/cpu/mcf5445x/Makefile
@@ -25,7 +25,7 @@
 
 # CFLAGS += -DET_DEBUG
 
-LIB	= lib$(CPU).o
+LIB	= $(obj)lib$(CPU).o
 
 START	= start.o
 COBJS	= cpu.o speed.o cpu_init.o interrupts.o pci.o