be2net: Declare some u16 fields as u32 to improve performance

When 16-bit integers are loaded on CPUs with high order native
register sizes, the CPU could use some extra ops before using them.
And currently some of the frequently used fields in the driver like
the producer and consumer indices of the queues are declared as u16.

This patch declares such fields as u32.  With this change we see the
64-byte packets per second numbers improve by about 4%.

Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>