wifi: ath11k: Remove unused declarations

Commit 2c3960c2 ("ath11k: setup ce tasklet for control path")
declared but never implemented ath11k_ce_map_service_to_pipe().
Commit e3396b8b ("ath11k: ce: support different CE configurations")
declared but never implemented ath11k_ce_attr_attach().
Commit d5c65159 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
declared but never implemented ath11k_qmi_event_work()/ath11k_qmi_msg_recv_work().

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230811104413.33668-1-yuehaibing@huawei.com