riscv: mm: Properly forward vmemmap_populate() altmap parameter

Make sure that the altmap parameter is properly passed on to
vmemmap_populate_hugepages().
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20240605114100.315918-2-bjorn@kernel.orgSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/mm/init.c

@@ -1438,7 +1438,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 	 * memory hotplug, we are not able to update all the page tables with
 	 * the new PMDs.
 	 */
-	return vmemmap_populate_hugepages(start, end, node, NULL);
+	return vmemmap_populate_hugepages(start, end, node, altmap);
 }
 #endif