qlge: Optimize rx buffer refill process.

RX Buffers are refilled in chunks of 16 at a time before notifying the
hardware with a register write.  This can cause several writes to take
place in a given napi poll call.  This change causes the write to take place
only once at the end of the call.

Signed-off-by: Ron Mercer <ron.mercer@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>