ath10k: fix return value for btcoex and peer stats debugfs

Return value is incorrect for btcoex and peer stats debugfs
'write' entries if the user provides a value that matches with
the already available debugfs entry, this results in the debugfs
entry getting stuck and the operation has to be terminated manually.
Fix this by returning the appropriate return 'count' as we do it for
other debugfs entries like pktlog etc.

Fixes: cc61a1bb ("ath10k: enable debugfs provision to enable Peer Stats feature")
Fixes: c28e6f06 ("ath10k: fix sanity check on enabling btcoex via debugfs")
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>