cxgb4: fix MAC address hash filter

Fix the calculation of the inexact hash-based MAC address filter.
It's 64 bits but current code is missing a ULL.  Results in filtering out
some legitimate packets.

Signed-off-by: Dimitris Michailidis <dm@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>