iwlwifi: mvm: take mutex for calling iwl_mvm_get_sync_time()

We need to take the mutex to call iwl_mvm_get_sync_time(), do it.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20210115130252.4bb5ccf881a6.I62973cbb081e80aa5b0447a5c3b9c3251a65cf6b@changeid

drivers/net/wireless/intel/iwlwifi/mvm/debugfs-vif.c

@@ -459,7 +459,10 @@ static ssize_t iwl_dbgfs_os_device_timediff_read(struct file *file,
 	const size_t bufsz = sizeof(buf);
 	int pos = 0;
 
+	mutex_lock(&mvm->mutex);
 	iwl_mvm_get_sync_time(mvm, &curr_gp2, &curr_os);
+	mutex_unlock(&mvm->mutex);
+
 	do_div(curr_os, NSEC_PER_USEC);
 	diff = curr_os - curr_gp2;
 	pos += scnprintf(buf + pos, bufsz - pos, "diff=%lld\n", diff);