PM: hibernate: Fix writing maj:min to /sys/power/resume

resume_store() first calls lookup_bdev() and after tries to handle
maj:min, but it does not reset the error before, hence if you will write
maj:min you will get ENOENT:

    # echo 259:2 >| /sys/power/resume
    bash: echo: write error: No such file or directory

This also should fix hiberation via systemd, since it uses this way.

Fixes: 1e8c813 ("PM: hibernate: don't use early_lookup_bdev in resume_store")
Signed-off-by: Azat Khuzhin <a3at.mail@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[ rjw: Subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

kernel/power/hibernate.c

@@ -1179,6 +1179,7 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,
 		unsigned maj, min, offset;
 		char *p, dummy;
 
+		error = 0;
 		if (sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2 ||
 		    sscanf(name, "%u:%u:%u:%c", &maj, &min, &offset,
 				&dummy) == 3) {