liquidio: remove duplicate code

Remove code duplicated in PF and VF; define that code once only in a common
header file included by PF and VF.

Signed-off-by: Satanand Burla <satananda.burla@cavium.com>
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>