smsc95xx: fix suspend buffer overflow

This patch fixes a buffer overflow introduced by bbd9f9e, where
the filter_mask array is accessed beyond its bounds.

Updated to also add a check for kzalloc failure, as reported by
Bjorn Mork and Joe Perches.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steve Glendinning <steve.glendinning@shawell.net>
Cc: Bjorn Mork <bjorn@mork.no>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>