cifs: convert to use ERR_CAST()

Use ERR_CAST() as it is designed for casting an error pointer to
another type.

This macro uses the __force and __must_check modifiers, which are used
to tell the compiler to check for errors where this macro is used.
Signed-off-by: Yuesong Li <liyuesong@vivo.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/connect.c

@@ -4081,7 +4081,7 @@ __cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 
 	ses = cifs_get_smb_ses(master_tcon->ses->server, ctx);
 	if (IS_ERR(ses)) {
-		tcon = (struct cifs_tcon *)ses;
+		tcon = ERR_CAST(ses);
 		cifs_put_tcp_session(master_tcon->ses->server, 0);
 		goto out;
 	}