liquidio: with embedded f/w, issue droq credits before enablement

1. Issue credits BEFORE enabling DROQ's; this prevents PKTPF_ERR interrupt.

Signed-off-by: Rick Farrington <ricardo.farrington@cavium.com>
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>