ARM: at91/power/reset: fix Kconfig "depends on" directive

MACH_AT91 doesn't exist so we can't "depend" on it. Fix the typo
by using the proper ARCH_AT91 config option.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

drivers/power/reset/Kconfig

@@ -16,7 +16,7 @@ config POWER_RESET_AS3722
 
 config POWER_RESET_AT91_POWEROFF
 	bool "Atmel AT91 poweroff driver"
-	depends on MACH_AT91
+	depends on ARCH_AT91
 	default SOC_AT91SAM9 || SOC_SAMA5
 	help
 	  This driver supports poweroff for Atmel AT91SAM9 and SAMA5
@@ -24,7 +24,7 @@ config POWER_RESET_AT91_POWEROFF
 
 config POWER_RESET_AT91_RESET
 	bool "Atmel AT91 reset driver"
-	depends on MACH_AT91
+	depends on ARCH_AT91
 	default SOC_AT91SAM9 || SOC_SAMA5
 	help
 	  This driver supports restart for Atmel AT91SAM9 and SAMA5