ath10k: fix error while writing 'simulate_fw_crash' debugfs

Fix invalid argument error while writing 'simulate_fw_crash',
though the funcionality is working fine we get an error 'invalid
argument' because 'count' value is not returned properly
(no reason to reduce the count value for removing the newline)

Fixes the below write error:

/sys/kernel/debug/ieee80211/phy0/ath10k# echo hw-restart >
simulate_fw_crash
-bash: echo: write error: Invalid argument

Also move the 'conf_mutex' as it is really not required for
fetching the userspace buffer.

Reported-by: Maharaja Kennadyrajan <c_mkenna@qti.qualcomm.com>
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qti.qualcomm.com>
Signed-off-by: Maharaja Kennadyrajan <c_mkenna@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath10k/debug.c

@@ -609,25 +609,23 @@ static ssize_t ath10k_write_simulate_fw_crash(struct file *file,
 	char buf[32];
 	int ret;
 
-	mutex_lock(&ar->conf_mutex);
-
 	simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, user_buf, count);
 
 	/* make sure that buf is null terminated */
 	buf[sizeof(buf) - 1] = 0;
 
+	/* drop the possible '\n' from the end */
+	if (buf[count - 1] == '\n')
+		buf[count - 1] = 0;
+
+	mutex_lock(&ar->conf_mutex);
+
 	if (ar->state != ATH10K_STATE_ON &&
 	    ar->state != ATH10K_STATE_RESTARTED) {
 		ret = -ENETDOWN;
 		goto exit;
 	}
 
-	/* drop the possible '\n' from the end */
-	if (buf[count - 1] == '\n') {
-		buf[count - 1] = 0;
-		count--;
-	}
-
 	if (!strcmp(buf, "soft")) {
 		ath10k_info(ar, "simulating soft firmware crash\n");
 		ret = ath10k_wmi_force_fw_hang(ar, WMI_FORCE_FW_HANG_ASSERT, 0);