powerpc/sgy_cts1000: Fix gpio_halt_cb()'s signature

Halt callback in struct machdep_calls is declared with __noreturn
attribute, so omitting that attribute in gpio_halt_cb()'s signatrue
results in compilation error.

Change the signature to address the problem as well as change the code
of the function to avoid ever returning from the function.
Signed-off-by: NAndrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: NScott Wood <oss@buserror.net>

arch/powerpc/platforms/85xx/sgy_cts1000.c

@@ -38,18 +38,18 @@ static void gpio_halt_wfn(struct work_struct *work)
 }
 static DECLARE_WORK(gpio_halt_wq, gpio_halt_wfn);
 
-static void gpio_halt_cb(void)
+static void __noreturn gpio_halt_cb(void)
 {
 	enum of_gpio_flags flags;
 	int trigger, gpio;
 
 	if (!halt_node)
-		return;
+		panic("No reset GPIO information was provided in DT\n");
 
 	gpio = of_get_gpio_flags(halt_node, 0, &flags);
 
 	if (!gpio_is_valid(gpio))
-		return;
+		panic("Provided GPIO is invalid\n");
 
 	trigger = (flags == OF_GPIO_ACTIVE_LOW);
 
@@ -57,6 +57,8 @@ static void gpio_halt_cb(void)
 
 	/* Probably wont return */
 	gpio_set_value(gpio, trigger);
+
+	panic("Halt failed\n");
 }
 
 /* This IRQ means someone pressed the power button and it is waiting for us