list: test: Add a test for list_is_head()

list: test: Add a test for list_is_head()

commit 37dc573c0a547e1aed0c9abb480fab797bd3833f upstream.

list_is_head() was added recently[1], and didn't have a KUnit test. The
implementation is trivial, so it's not a particularly exciting test, but
it'd be nice to get back to full coverage of the list functions.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/list.h?id=0425473037db40d9e322631f2d4dc6ef51f97e88

Signed-off-by: David Gow <davidgow@google.com>
Acked-by: Daniel Latypov <dlatypov@google.com>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>