powerpc/xive: 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 xive_off() and
xive_store_eoi_cmdline().

Fixes: 243e251 ("powerpc/xive: Native exploitation of the XIVE interrupt controller")
Fixes: c21ee04 ("powerpc/xive: Add a kernel parameter for StoreEOI")
[lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru]
Reported-by: Igor Zhbanov <i.zhbanov@omprussia.ru>:
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220313065936.4363-1-rdunlap@infradead.org

Author: rddunlap

arch/powerpc/sysdev/xive/common.c

@@ -1708,20 +1708,20 @@ __be32 *xive_queue_page_alloc(unsigned int cpu, u32 queue_shift)
 static int __init xive_off(char *arg)
 {
 	xive_cmdline_disabled = true;
-	return 0;
+	return 1;
 }
 __setup("xive=off", xive_off);
 
 static int __init xive_store_eoi_cmdline(char *arg)
 {
 	if (!arg)
-		return -EINVAL;
+		return 1;
 
 	if (strncmp(arg, "off", 3) == 0) {
 		pr_info("StoreEOI disabled on kernel command line\n");
 		xive_store_eoi = false;
 	}
-	return 0;
+	return 1;
 }
 __setup("xive.store-eoi=", xive_store_eoi_cmdline);