recipetool: ignore incidental kernel module source

If the source tree happens to contain a kernel module as an example, a
test or under a "contrib" directory then we shouldn't be picking it up
and making the determination that the entire thing is a kernel module.

An example that triggered this is zstd, which ships a kernel module
under contrib/linux-kernel:

  https://github.com/facebook/zstd

(From OE-Core rev: c2b3154158d4bb0855daa56477393341139d4cf9)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/recipetool/create_kmod.py

@@ -40,7 +40,7 @@ class KernelModuleRecipeHandler(RecipeHandler):
 
         makefiles = []
 
-        files = RecipeHandler.checkfiles(srctree, ['*.c', '*.h'], recursive=True)
+        files = RecipeHandler.checkfiles(srctree, ['*.c', '*.h'], recursive=True, excludedirs=['contrib', 'test', 'examples'])
         if files:
             for cfile in files:
                 # Look in same dir or parent for Makefile