amt: fix typo in comment

Correct spelling on 'non-existent' in comment

Signed-off-by: Ruffalo Lavoisier <RuffaloLavoisier@gmail.com>
Link: https://lore.kernel.org/r/20220728032854.151180-1-RuffaloLavoisier@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>