This patch adds support to allocate gigantic hugepages using CMA by
specifying the hugetlb_cma= kernel parameter.  This is only supported on
RV64.
Reviewed-by: Alexandre Ghiti <alex@ghiti.fr>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>