qed: Add statistics support

Device statistics can be gathered on-demand. This adds the qed support for
reading the statistics [both function and port] from the device, and adds
to the public API a method for requesting the current statistics.

Signed-off-by: Manish Chopra <Manish.Chopra@qlogic.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: Ariel Elior <Ariel.Elior@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>