kunit: tool: drop unused KernelDirectoryPath var

Commit be886ba9 ("kunit: run kunit_tool from any directory")
introduced this variable, but it was unused even in that commit.

Since it's still unused now and callers can instead use
get_kernel_root_path(), delete this var.
Signed-off-by: NDaniel Latypov <dlatypov@google.com>
Reviewed-by: NDavid Gow <davidgow@google.com>
Reviewed-by: NBrendan Higgins <brendanhiggins@google.com>
Signed-off-by: NShuah Khan <skhan@linuxfoundation.org>

tools/testing/kunit/kunit.py

@@ -63,8 +63,6 @@ class KunitRequest(KunitExecRequest, KunitBuildRequest):
 	pass
 
 
-KernelDirectoryPath = sys.argv[0].split('tools/testing/kunit/')[0]
-
 def get_kernel_root_path() -> str:
 	path = sys.argv[0] if not __file__ else __file__
 	parts = os.path.realpath(path).split('tools/testing/kunit')