bnxt_en: Support for 64-bit flow handle.

Older firmware only supports 16-bit flow handle, because of which the
number of flows that can be offloaded can’t scale beyond a point.
Newer firmware supports 64-bit flow handle enabling the host to scale
upto millions of flows. With the new 64-bit flow handle support, driver
has to query flow stats in a different way compared to the older approach.

This patch adds support for 64-bit flow handle and new way to query
flow stats.

Signed-off-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Reviewed-by: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>