wifi: ath10k: Fix an error code problem in ath10k_dbg_sta_write_peer_debug_trigger()

Clang Static Checker (scan-build) warns:

drivers/net/wireless/ath/ath10k/debugfs_sta.c:line 429, column 3
Value stored to 'ret' is never read.

Return 'ret' rather than 'count' when 'ret' stores an error code.

Fixes: ee8b08a1 ("ath10k: add debugfs support to get per peer tids log via tracing")
Signed-off-by: Su Hui <suhui@nfschina.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240422034243.938962-1-suhui@nfschina.com