bnx2x: simplify distinction between port and func stats

The 'flags' field in bnx2x_stats_arr[] serves only one purpose - to tell
us if the statistic is a per-port stat and thus should not be shown for
virtual functions. It's strange that the field can have three different
values. A boolean will do just fine.

Also remove IS_FUNC_STAT(). It was used only once and it's in fact just
a negation of IS_PORT_STAT().

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>