linux-yocto: restore WORKDIR as a patch source directory

In the switch to using src_patches and using patches in their
source directory, the scanning of WORKDIR migrated items like
config fragments was dropped. Adding WORKDIR back as a patch
directory restores the old functionality.

(From OE-Core rev: fd46d2ec75a53a02464ab2f0bc69eb1971432c9a)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/kernel-yocto.bbclass

@@ -92,6 +92,8 @@ do_patch() {
 		fi
 	done
 
+	patch_dirs="${patch_dirs} ${WORKDIR}"
+
 	# add any explicitly referenced features onto the end of the feature
 	# list that is passed to the kernel build scripts.
 	if [ -n "${KERNEL_FEATURES}" ]; then