can: avoids a false warning

can: avoids a false warning

At this point optlen == sizeof(sfilter) but some compilers are dumb.

Reported-by: Németh Márton <nm127@freemail.h
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Oliver Hartkopp <oliver@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Upstream commit:
http://git.kernel.org/?p=linux/kernel/git/davem/net-next-2.6.git;a=commitdiff;h=4ffa87012efd7b664762b579213d4663560ef4a3

git-svn-id: svn://svn.berlios.de//socketcan/trunk@1258 030b6a49-0b11-0410-94ab-b0dab22257f2