ifd->offset is unsigned.  gigaset_isowbuf_getbytes() may return signed
unnoticed.  Revised version of patch originally submitted by Roel Kluin
<12o3l@tiscali.nl>.
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>