i40evf: fix write flush
i40evf: fix write flush

For i40e vf driver, should use I40EVF_WRITE_FLUSH to flush
configuration but not I40E_WRITE_FLUSH. This patch fixed this issue.

Fixes: be6c228d4da3 (i40evf: support Rx interrupt)

Reported-by: Qian Xu <81156ea8c687d383f58bd067d87c20618b5afdb1@intel.com>
Signed-off-by: Jingjing Wu <64d28b617c3b4840f5ded1bfa611cba7fadfe5c7@intel.com>
Acked-by: Helin Zhang <aba9dfdb1a6ec8bf1ff66b95272c029f8dfde1b1@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk