power: supply: test_power: add missing newlines when printing parameters by sysfs

When I cat some module parameters by sysfs, it displays as follows.
It's better to add a newline for easy reading.

root@syzkaller:~# cd /sys/module/test_power/parameters/
root@syzkaller:/sys/module/test_power/parameters# cat ac_online
onroot@syzkaller:/sys/module/test_power/parameters# cat battery_present
trueroot@syzkaller:/sys/module/test_power/parameters# cat battery_health
goodroot@syzkaller:/sys/module/test_power/parameters# cat battery_status
dischargingroot@syzkaller:/sys/module/test_power/parameters# cat battery_technology
LIONroot@syzkaller:/sys/module/test_power/parameters# cat usb_online
onroot@syzkaller:/sys/module/test_power/parameters#

Signed-off-by: Xiongfeng Wang <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/test_power.c

···
 static int param_get_ac_online(char *buffer, const struct kernel_param *kp)
 {
 	strcpy(buffer, map_get_key(map_ac_online, ac_online, "unknown"));
+	strcat(buffer, "\n");
 	return strlen(buffer);
 }
 
···
 static int param_get_usb_online(char *buffer, const struct kernel_param *kp)
 {
 	strcpy(buffer, map_get_key(map_ac_online, usb_online, "unknown"));
+	strcat(buffer, "\n");
 	return strlen(buffer);
 }
 
···
 static int param_get_battery_status(char *buffer, const struct kernel_param *kp)
 {
 	strcpy(buffer, map_get_key(map_status, battery_status, "unknown"));
+	strcat(buffer, "\n");
 	return strlen(buffer);
 }
 
···
 static int param_get_battery_health(char *buffer, const struct kernel_param *kp)
 {
 	strcpy(buffer, map_get_key(map_health, battery_health, "unknown"));
+	strcat(buffer, "\n");
 	return strlen(buffer);
 }
 
···
 					const struct kernel_param *kp)
 {
 	strcpy(buffer, map_get_key(map_present, battery_present, "unknown"));
+	strcat(buffer, "\n");
 	return strlen(buffer);
 }
 
···
 {
 	strcpy(buffer,
 		map_get_key(map_technology, battery_technology, "unknown"));
+	strcat(buffer, "\n");
 	return strlen(buffer);
 }