net: stmmac: fix return value of __setup handler

__setup() handlers should return 1 on success, i.e., the parameter
has been handled. A return of 0 causes the "option=value" string to be
added to init's environment strings, polluting it.

Fixes: 47dd7a54 ("net: add support for STMicroelectronics Ethernet controllers.")
Fixes: f3240e28 ("stmmac: remove warning when compile as built-in (V2)")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Igor Zhbanov <i.zhbanov@omprussia.ru>
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Jose Abreu <joabreu@synopsys.com>
Link: https://lore.kernel.org/r/20220224033536.25056-1-rdunlap@infradead.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -7491,7 +7491,7 @@ static int __init stmmac_cmdline_opt(char *str)
 	char *opt;
 
 	if (!str || !*str)
-		return -EINVAL;
+		return 1;
 	while ((opt = strsep(&str, ",")) != NULL) {
 		if (!strncmp(opt, "debug:", 6)) {
 			if (kstrtoint(opt + 6, 0, &debug))
@@ -7522,11 +7522,11 @@ static int __init stmmac_cmdline_opt(char *str)
 				goto err;
 		}
 	}
-	return 0;
+	return 1;
 
 err:
 	pr_err("%s: ERROR broken module parameter conversion", __func__);
-	return -EINVAL;
+	return 1;
 }
 
 __setup("stmmaceth=", stmmac_cmdline_opt);