Refactor: Move serialize to ubi

Functions in serialize are specific to UBI, move it to ubi dir.

Tested: On the last commit of the patch series, run code update and
        factory reset on Witherspoon and all work fine.

Change-Id: I9176e638d9f3bfe0d424b57f8da4667a751cb5bd
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/test/Makefile.am b/test/Makefile.am
index c4165ec..1a94d0d 100755
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -33,7 +33,7 @@
 utest_LDADD = \
 	$(top_builddir)/openpower_update_manager-activation.o \
 	$(top_builddir)/openpower_update_manager-version.o \
-	$(top_builddir)/openpower_update_manager-serialize.o \
+	$(top_builddir)/ubi/openpower_update_manager-serialize.o \
 	$(top_builddir)/ubi/openpower_update_manager-watch.o \
 	$(top_builddir)/openpower_update_manager-item_updater.o \
 	$(top_builddir)/org/openbmc/Associations/openpower_update_manager-server.o \