Since tty->index is signed and may be < 0, we should assign this to int not
uint.  There is already a check to ensure if it is not negative, but gcc
complains with -W flag enabled and it is perfectly correct:
drivers/char/isicom.c:953: warning: comparison of unsigned expression < 0
is always false

Fix this issue by converting `line' variable from uint to int.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>