atheros/atl1c:fix repeated words in comments

Delete the redundant word 'slot'.

Signed-off-by: Jilin Yuan <yuanjilin@cdjrlc.com>
Link: https://lore.kernel.org/r/20220629081632.54445-1-yuanjilin@cdjrlc.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>