SPL: lib/Makefile: Add crc32.c to SPL build

This is needed for the SPEAr SPL support, as SPEAr uses the mkimage
header to wrap and validate the images (SPL & U-Boot).

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/lib/Makefile b/lib/Makefile
index 556601c..c60c380 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -37,7 +37,6 @@
 COBJS-$(CONFIG_USB_TTY) += circbuf.o
 COBJS-y += crc7.o
 COBJS-y += crc16.o
-COBJS-y += crc32.o
 COBJS-y += display_options.o
 COBJS-y += errno.o
 COBJS-$(CONFIG_OF_CONTROL) += fdtdec.o
@@ -60,6 +59,7 @@
 ifdef CONFIG_SPL_BUILD
 COBJS-$(CONFIG_SPL_YMODEM_SUPPORT) += crc16.o
 endif
+COBJS-y += crc32.o
 COBJS-y += ctype.o
 COBJS-y += div64.o
 COBJS-y += string.o