mpipe: fix link initialization ordering

mpipe: fix link initialization ordering

Mpipe link structure is initialized in function mpipe_link_init().
Currently it's only called from the eth_dev_ops.dev_start, which
caused crashes when link mgmt APIs (like promiscuous_enable)
was called before eth_dev_ops.dev_start(). This submit fixed it
by calling mpipe_link_init() in rte_pmd_mpipe_devinit().

Fixes: a8dd50513dea ("mpipe: add TILE-Gx mPIPE poll mode driver")

Signed-off-by: Liming Sun <lsun@ezchip.com>
Acked-by: Zhigang Lu <zlu@ezchip.com>