checkpatch: correct spelling in kfree checks

Correct spelling in the kfree reports.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>