drivers: net: xgene: fix register offset

drivers: net: xgene: fix register offset

BugLink: https://launchpad.net/bugs/1632739
This patch fixes SG_RX_DV_GATE_REG_0_ADDR register offset
and ring state field lengths.

Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Tested-by: Toan Le <toanle@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit e2f2d9a72605666ec772c865dbe89edbab896d27 yakkety)
Signed-off-by: Craig Magina <craig.magina@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>