RDMA/iw_cxgb4: allocate enough space for debugfs "qps" dump

With IPv6 addresses, the "qps" debugfs is running out of space and
truncating the output.  Bump the required size accordingly.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>