Fix unused variable warning when CONFIG_CIFS_POSIX disabled.
   fs/cifs/ioctl.c: In function 'cifs_ioctl':
>> fs/cifs/ioctl.c:40:8: warning: unused variable 'ExtAttrMask' [-Wunused-variable]
     __u64 ExtAttrMask = 0;
           ^
Pointed out by 0-DAY kernel build testing backend
Signed-off-by: Steve French <smfrench@gmail.com>
        struct cifsFileInfo *pSMBFile = filep->private_data;
        struct cifs_tcon *tcon;
        __u64   ExtAttrBits = 0;
-       __u64   ExtAttrMask = 0;
        __u64   caps;
 
        xid = get_xid();
                        caps = le64_to_cpu(tcon->fsUnixInfo.Capability);
 #ifdef CONFIG_CIFS_POSIX
                        if (CIFS_UNIX_EXTATTR_CAP & caps) {
+                               __u64   ExtAttrMask = 0;
                                rc = CIFSGetExtAttr(xid, tcon,
                                                    pSMBFile->fid.netfid,
                                                    &ExtAttrBits, &ExtAttrMask);