wlcore: fix runtime pm imbalance in wlcore_irq_locked

When wlcore_fw_status() returns an error code, a pairing
runtime PM usage counter decrement is needed to keep the
counter balanced. It's the same for all error paths after
wlcore_fw_status().

Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200522044906.29564-1-dinghao.liu@zju.edu.cn