linux-yocto: fix SRC_URI patching with unified repos

As reported by Paul Barker, my attempt to allow the patching
of kernel meta data broke other repository configurations, since
the meta data patch routing was matching too broadly and the
same repo would end up being patched twice.

Using his suggested fix, we are up and running with both types
of repos again.

(From OE-Core rev: 0fd09633e3c2fb4668c7700516d288f8c5356ff6)

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

meta/classes/kernel-yocto.bbclass

@@ -15,7 +15,7 @@ def find_patches(d,subdir):
         patchdir = ''
         if "patchdir" in parm:
             patchdir = parm["patchdir"]
-        if patchdir:
+        if subdir:
             if subdir == patchdir:
                 patch_list.append(local)
         else: