cifs: fix static checker warning

Remove unnecessary NULL check of oparam->cifs_sb when parsing symlink
error response as it's already set by all smb2_open_file() callers and
deferenced earlier.

This fixes below report:

  fs/cifs/smb2file.c:126 smb2_open_file()
  warn: variable dereferenced before check 'oparms->cifs_sb' (see line 112)

Link: https://lore.kernel.org/r/Y0kt42j2tdpYakRu@kili
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Paulo Alcantara

fs/cifs/smb2file.c

@@ -123,7 +123,7 @@ int smb2_open_file(const unsigned int xid, struct cifs_open_parms *oparms, __u32
 
 		if (unlikely(!err_iov.iov_base || err_buftype == CIFS_NO_BUFFER))
 			rc = -ENOMEM;
-		else if (hdr->Status == STATUS_STOPPED_ON_SYMLINK && oparms->cifs_sb) {
+		else if (hdr->Status == STATUS_STOPPED_ON_SYMLINK) {
 			rc = smb2_parse_symlink_response(oparms->cifs_sb, &err_iov,
 							 &data->symlink_target);
 			if (!rc) {