IB/ipoib: Remove memset after vzalloc in ipoib_cm.c

vzalloc has already zeroed the memory.  So a memset is unneeded.

Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>