myri10ge: fix the number of interrupt slots

Fix a long-standing bug/misunderstanding between the
driver and the firmware.  The size of the interrupt
queue must be set to the number of rx slots (big + small),
and it should never have been a tunable.
Setting it too small results in chaos.

Signed-off-by: Brice Goglin <brice@myri.com>
Signed-off-by: Andrew Gallatin <gallatin@myri.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>