ath11k: fix missing skb drop on htc_tx_completion error

On htc_tx_completion error the skb is not dropped. This is wrong since
the completion_handler logic expect the skb to be consumed anyway even
when an error is triggered. Not freeing the skb on error is a memory
leak since the skb won't be freed anywere else. Correctly free the
packet on eid >= ATH11K_HTC_EP_COUNT before returning.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.5.0.1-01208-QCAHKSWPL_SILICONZ-1

Fixes: f951380a ("ath11k: Disabling credit flow for WMI path")
Signed-off-by: Christian 'Ansuel' Marangi <ansuelsmth@gmail.com>
Reviewed-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220528142516.20819-2-ansuelsmth@gmail.com