kernel.bbclass: Ensure kernel/* internal sysroot working directory don't get packaged

This removes a couple of megabytes of QA warnings!

(From OE-Core rev: 69c2f6f7a9133cc8d64560fefa42e5852322f716)

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

meta/classes/kernel.bbclass

@@ -168,6 +168,12 @@ kernel_do_install() {
 	done
 }
 
+PACKAGE_PREPROCESS_FUNCS += "kernel_package_preprocess"
+
+kernel_package_preprocess () {
+	rm -rf ${PKGD}/kernel
+}
+
 sysroot_stage_all_append() {
 	sysroot_stage_dir ${D}/kernel ${SYSROOT_DESTDIR}/kernel
 }