PCI/ASPM: Add missing newline in sysfs 'policy'

When I cat ASPM parameter 'policy' by sysfs, it displays as follows.  Add a
newline for easy reading.  Other sysfs attributes already include a
newline.

  [root@localhost ~]# cat /sys/module/pcie_aspm/parameters/policy
  [default] performance powersave powersupersave [root@localhost ~]#

Fixes: 7d715a6c ("PCI: add PCI Express ASPM support")
Link: https://lore.kernel.org/r/1594972765-10404-1-git-send-email-wangxiongfeng2@huawei.comSigned-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pcie/aspm.c

@@ -1182,6 +1182,7 @@ static int pcie_aspm_get_policy(char *buffer, const struct kernel_param *kp)
 			cnt += sprintf(buffer + cnt, "[%s] ", policy_str[i]);
 		else
 			cnt += sprintf(buffer + cnt, "%s ", policy_str[i]);
+	cnt += sprintf(buffer + cnt, "\n");
 	return cnt;
 }