cxgb4: move common filter code to separate file

Move common filter code to separate files.  Also fix the following
checkpatch checks.

CHECK: Comparison to NULL could be written "!f->l2t"
+               if (f->l2t == NULL) {

CHECK: spaces preferred around that '/' (ctx:VxV)
+       fwr->len16_pkd = htonl(FW_WR_LEN16_V(sizeof(*fwr)/16));

Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>