MIPS: BCM47XX: Simplify function looking for NVRAM entry

First of all it shouldn't modify copied NVRAM just to make sure it can
loop over all entries. It's enough to just compare current position
pointer with the end of buffer address.
Secondly buffer is guaranteed to be \0 ended, so we don't need strnchr.
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Hante Meuleman <meuleman@broadcom.com>
Cc: Ian Kent <raven@themaw.net>
Patchwork: https://patchwork.linux-mips.org/patch/10032/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/bcm47xx/nvram.c

@@ -171,7 +171,7 @@ static int nvram_init(void)
 int bcm47xx_nvram_getenv(const char *name, char *val, size_t val_len)
 {
 	char *var, *value, *end, *eq;
-	int data_left, err;
+	int err;
 
 	if (!name)
 		return -EINVAL;
@@ -184,19 +184,16 @@ int bcm47xx_nvram_getenv(const char *name, char *val, size_t val_len)
 
 	/* Look for name=value and return value */
 	var = &nvram_buf[sizeof(struct nvram_header)];
-	end = nvram_buf + sizeof(nvram_buf) - 2;
-	end[0] = '\0';
-	end[1] = '\0';
-	for (; *var; var = value + strlen(value) + 1) {
-		data_left = end - var;
-
-		eq = strnchr(var, data_left, '=');
+	end = nvram_buf + sizeof(nvram_buf);
+	while (var < end && *var) {
+		eq = strchr(var, '=');
 		if (!eq)
 			break;
 		value = eq + 1;
 		if (eq - var == strlen(name) &&
 		    strncmp(var, name, eq - var) == 0)
 			return snprintf(val, val_len, "%s", value);
+		var = value + strlen(value) + 1;
 	}
 	return -ENOENT;
 }