ath11k: Fix typo in comments

There is a typo(isn't') in comments.
It maybe 'isn't' instead of 'isn't''.

Signed-off-by: Zhang Jiaming <jiaming@nfschina.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220704030004.16484-1-jiaming@nfschina.com