release: Deinstall u-boot ports before installing

FORCE_PKG_REGISTER is broken so multiple invocation of release.sh for the
same board will fails if /scratch isn't cleaned.
Leave it but deinstall the package first.

Reviewed by:	gjb
Differential Revision:	https://reviews.freebsd.org/D16513

release/release.sh

@@ -307,7 +307,7 @@ extra_chroot_setup() {
 		for _PORT in ${EMBEDDEDPORTS}; do
 			eval chroot ${CHROOTDIR} env ${PBUILD_FLAGS} make -C \
 				/usr/ports/${_PORT} \
-				FORCE_PKG_REGISTER=1 install clean distclean
+				FORCE_PKG_REGISTER=1 deinstall install clean distclean
 		done
 	fi