recipes: Start WORKDIR -> UNPACKDIR transition

Replace references of WORKDIR with UNPACKDIR where it makes sense to do
so in preparation for changing the default value of UNPACKDIR.

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-multimedia/recipes-multimedia/libdvbcsa/libdvbcsa_1.1.0.bb

@@ -15,5 +15,5 @@ inherit autotools lib_package pkgconfig
 
 do_install:append() {
     install -D -m 0644 ${S}/src/dvbcsa/dvbcsa.h ${D}${includedir}/dvbcsa/dvbcsa.h
-    install -D -m 0644 ${WORKDIR}/libdvbcsa.pc ${D}${libdir}/pkgconfig/libdvbcsa.pc
+    install -D -m 0644 ${UNPACKDIR}/libdvbcsa.pc ${D}${libdir}/pkgconfig/libdvbcsa.pc
 }