RDMA/bnxt_re: Fix sizeof mismatch for allocation of pbl_tbl.

RDMA/bnxt_re: Fix sizeof mismatch for allocation of pbl_tbl.

An incorrect sizeof is being used, u64 * is not correct, it should be just
u64 for a table of umem_pgs number of u64 items in the pbl_tbl.  Use the
idiom sizeof(*pbl_tbl) to get the object type without the need to
explicitly use u64.

Link: https://lore.kernel.org/r/20201006114700.537916-1-colin.king@canonical.com
Addresses-Coverity: ("Sizeof not portable (SIZEOF_MISMATCH)")
Fixes: 1ac5a4047975 ("RDMA/bnxt_re: Add bnxt_re RoCE driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>