RDMA/vmw_pvrdma: Use more specific sizeof in kcalloc

Convert the sizeof(void *) in two kcalloc calls to be more
specific for the arrays that are being allocated.

Reviewed-by: Adit Ranadive <aditr@vmware.com>
Reviewed-by: Aditya Sarwade <asarwade@vmware.com>
Reviewed-by: Jorgen Hansen <jhansen@vmware.com>
Signed-off-by: Bryan Tan <bryantan@vmware.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>