device-dax: Fix default return code of range_parse()

The return value of range_parse() indicates the size when it is
positive.  The error code should be negative.
Signed-off-by: NShiyang Ruan <ruansy.fnst@cn.fujitsu.com>
Reviewed-by: NJoao Martins <joao.m.martins@oracle.com>
Link: https://lore.kernel.org/r/20210126021331.1059933-1-ruansy.fnst@cn.fujitsu.comReported-by: NZhang Qilong <zhangqilong3@huawei.com>
Fixes: 8490e2e2 ("device-dax: add a range mapping allocation attribute")
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/dax/bus.c

@@ -1038,7 +1038,7 @@ static ssize_t range_parse(const char *opt, size_t len, struct range *range)
 {
 	unsigned long long addr = 0;
 	char *start, *end, *str;
-	ssize_t rc = EINVAL;
+	ssize_t rc = -EINVAL;
 
 	str = kstrdup(opt, GFP_KERNEL);
 	if (!str)