MFC r341528:
ibcore: Always check return value from ib_init_ah_from_wc().

This prevents code from accepting RoCEv1 connections when
only ROCEv2 is enabled and vice versa.

Linux commit:
0c4386ec77cfcd0ccbdbe8c2e67dd3a49b2a4c7f

Sponsored by: Mellanox Technologies