powerpc/idle: Fix return value of __setup() handler

__setup() handlers should return 1 to obsolete_checksetup() in
init/main.c to indicate that the boot option has been handled.

A return of 0 causes the boot option/value to be listed as an Unknown
kernel parameter and added to init's (limited) argument or environment
strings.

Also, error return codes don't mean anything to obsolete_checksetup() --
only non-zero (usually 1) or zero. So return 1 from powersave_off().

Fixes: 302eca18 ("[POWERPC] cell: use ppc_md->power_save instead of cbe_idle_loop")
Reported-by: Igor Zhbanov <izh1979@gmail.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220502192925.19954-1-rdunlap@infradead.org

arch/powerpc/kernel/idle.c

@@ -37,7 +37,7 @@ static int __init powersave_off(char *arg)
 {
 	ppc_md.power_save = NULL;
 	cpuidle_disable = IDLE_POWERSAVE_OFF;
-	return 0;
+	return 1;
 }
 __setup("powersave=off", powersave_off);