IB/hfi1: Suppress a compiler warning

Avoid that the following compiler warning is reported when building
with gcc 8:

drivers/infiniband/hw/hfi1/verbs.c:1896:2: warning: 'strncpy' output may be truncated copying 64 bytes from a string of length 64 [-Wstringop-truncation]

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>