ixgbe: check host interface return status

Writing to read-only fields returns a non-OK Return Status
for shadow RAM write command for X550.
This information was previously discarded.

Signed-off-by: Stanislaw Grzeszczak <stanislaw.a.grzeszczak@intel.com>
Signed-off-by: Guinan Sun <guinanx.sun@intel.com>
Reviewed-by: Wei Zhao <wei.zhao1@intel.com>

Approved by: imp
Obtained from: DPDK (db18e37090a3b9af47d6a6886248520f6b220bf9)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D31621