wifi: ath9k: remove redundant assignment to variable ret

The variable ret is being assigned a value but it isn't being
read afterwards. The assignment is redundant and so ret can be
removed.

Cleans up clang scan build warning:
warning: Although the value stored to 'ret' is used in the
enclosing expression, the value is never actually read from
'ret' [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240116155452.2315351-1-colin.i.king@gmail.com