power: reset: at91-poweroff: fix clobber list

Assembly in at91_lpddr_poweroff has r0 in the clobber list but uses r6.
Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

drivers/power/reset/at91-poweroff.c

@@ -97,7 +97,7 @@ static void at91_lpddr_poweroff(void)
 		  "r" cpu_to_le32(AT91_DDRSDRC_LPDDR2_PWOFF),
 		  "r" (at91_shdwc_base),
 		  "r" cpu_to_le32(AT91_SHDW_KEY | AT91_SHDW_SHDW)
-		: "r0");
+		: "r6");
 }
 
 static int at91_poweroff_get_wakeup_mode(struct device_node *np)