ath10k: use the right length of "background"

commit 31b23982 upstream.

The word "background" contains 10 characters so the third argument of
strncmp() need to be 10 in order to match this prefix correctly.
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Fixes: 855aed12 ("ath10k: add spectral scan feature")
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -338,7 +338,7 @@ static ssize_t write_file_spec_scan_ctl(struct file *file,
 		} else {
 			res = -EINVAL;
 		}
-	} else if (strncmp("background", buf, 9) == 0) {
+	} else if (strncmp("background", buf, 10) == 0) {
 		res = ath10k_spectral_scan_config(ar, SPECTRAL_BACKGROUND);
 	} else if (strncmp("manual", buf, 6) == 0) {
 		res = ath10k_spectral_scan_config(ar, SPECTRAL_MANUAL);