igb: change type for ring sizes to u16 in igb_set_ring_param

Change the type for the ring size values to u16 and use min/max_t instead of
min/max.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>