recipes: Ensure S is set to a valid directory

Several recipes have S pointing at a directory that does not exist.
Set S in these cases to somethig valid making the metadata and
recipe behaviour more consistent.

Tweak one of the QA test diff offsets to match the changed recipe.

(From OE-Core rev: 22f1f5849a9a3bf287dbe8933546e52e39ddc86e)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-kernel/dtc/python3-dtschema-wrapper_2021.10.bb

@@ -7,6 +7,9 @@ SRC_URI = "file://dt-doc-validate \
            file://dt-mk-schema \
            file://dt-validate"
 
+S = "${WORKDIR}/sources"
+UNPACKDIR = "${S}"
+
 do_install() {
     install -d ${D}${bindir}/
     install -m 755 ${UNPACKDIR}/dt-doc-validate ${D}${bindir}/