ARM: at91: pm: wait for ddr power mode off

Wait for DDR power mode off before shutting down the core.
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210415105010.569620-16-claudiu.beznea@microchip.com

arch/arm/mach-at91/pm_suspend.S

@@ -980,6 +980,11 @@ ulp_exit:
 	mov	tmp1, #0x1
 	str	tmp1, [r0, #0x10]
 
+	/* Wait for it. */
+1:	ldr	tmp1, [r0, #0x10]
+	tst	tmp1, #0x1
+	beq	1b
+
 	/* Shutdown */
 	ldr	r0, .shdwc
 	mov	tmp1, #0xA5000000