wifi: ath10k: Remove the unused function ath10k_ce_shadow_src_ring_write_index_set()

The function ath10k_ce_shadow_src_ring_write_index_set is defined in the
ce.c file, but not called elsewhere, so remove this unused function.

drivers/net/wireless/ath/ath10k/ce.c:212:1: warning: unused function 'ath10k_ce_shadow_dest_ring_write_index_set'.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=3519


Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20221219132041.91418-1-jiapeng.chong@linux.alibaba.com