styhead: update WORKDIR usage

The latest yocto release(styhead,5.1) has made a significant change[1]
to the use of the WORKDIR parameter.

This is not the complete change required but gets us going in the right
direction.

[1]: https://docs.yoctoproject.org/next/migration-guides/migration-5.1.html#workdir-changes

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I4f184b361be69e7704a0657a4a00cdad981aff8a
diff --git a/meta-google/recipes-extended/networking/mstpd_git.bb b/meta-google/recipes-extended/networking/mstpd_git.bb
index 923197b..8078081 100644
--- a/meta-google/recipes-extended/networking/mstpd_git.bb
+++ b/meta-google/recipes-extended/networking/mstpd_git.bb
@@ -23,8 +23,8 @@
   rmdir ${D}${libdir} || true
 
   install -d -m 0755 ${D}/${sbindir}
-  install -m 0755 ${WORKDIR}/bridge-stp ${D}/${sbindir}
+  install -m 0755 ${UNPACKDIR}/bridge-stp ${D}/${sbindir}
 
   install -d -m 0755 ${D}${systemd_system_unitdir}
-  install -m 0644 ${WORKDIR}/mstpd.service ${D}${systemd_system_unitdir}/
+  install -m 0644 ${UNPACKDIR}/mstpd.service ${D}${systemd_system_unitdir}/
 }