ath11k: Remove unused inline function htt_htt_stats_debug_dump()

There is no caller in tree, so can remove it.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200909134533.19604-1-yuehaibing@huawei.com