ath9k: Remove unnecessary print function dev_err()

The print function dev_err() is redundant because
platform_get_irq_byname() already prints an error.

Eliminate the follow coccicheck warning:
./drivers/net/wireless/ath/ath9k/ahb.c:103:2-9: line 103 is redundant
because platform_get_irq() already prints an error

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220408000113.129906-2-yang.lee@linux.alibaba.com