btrfs: remove useless ACL check

posix_acl_xattr_set() already does the check, and it's the only
way to feed in an ACL from userspace.
So the check here is useless, remove it.

Signed-off-by: zhang zhen <[e-mail]>
Signed-off-by: Chris Mason <[e-mail]>

fs/btrfs/acl.c

···
 	const char *name;
 	char *value = NULL;
 
-	if (acl) {
-		ret = posix_acl_valid(acl);
-		if (ret < 0)
-			return ret;
-		ret = 0;
-	}
-
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name = POSIX_ACL_XATTR_ACCESS;