ARM: at91: pm: remove pm_bu initialization in at91_pm_backup_init()

There is no need to initialize pm_bu since it is used only if backup
mode is selected. In case backup mode initialization fails (which means
pm_bu is invalid) the ULP0 mode will be selected.
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

arch/arm/mach-at91/pm.c

@@ -580,8 +580,6 @@ static int __init at91_pm_backup_init(void)
 	if (!at91_is_pm_mode_active(AT91_PM_BACKUP))
 		return 0;
 
-	pm_bu = NULL;
-
 	np = of_find_compatible_node(NULL, NULL, "atmel,sama5d2-sfrbu");
 	if (!np) {
 		pr_warn("%s: failed to find sfrbu!\n", __func__);
@@ -590,7 +588,6 @@ static int __init at91_pm_backup_init(void)
 
 	pm_data.sfrbu = of_iomap(np, 0);
 	of_node_put(np);
-	pm_bu = NULL;
 
 	np = of_find_compatible_node(NULL, NULL, "atmel,sama5d2-securam");
 	if (!np)