yalla: fix passing on-demand mapping config to mxm.

ompi/mca/pml/yalla/pml_yalla.c

@@ -109,13 +109,13 @@ int mca_pml_yalla_open(void)
          opal_mem_hooks_support_level()))
     {
         PML_YALLA_VERBOSE(1, "enabling on-demand memory mapping");
-        opal_setenv("MXM_PML_MEM_ON_DEMAND_MAP", "y", false, &environ);
+        opal_setenv("MXM_MPI_MEM_ON_DEMAND_MAP", "y", false, &environ);
         ompi_pml_yalla.using_mem_hooks = 1;
     } else {
         PML_YALLA_VERBOSE(1, "disabling on-demand memory mapping");
         ompi_pml_yalla.using_mem_hooks = 0;
     }
-    opal_setenv("MXM_PML_SINGLE_THREAD", ompi_mpi_thread_multiple ? "n" : "y",
+    opal_setenv("MXM_MPI_SINGLE_THREAD", ompi_mpi_thread_multiple ? "n" : "y",
                 false, &environ);
 
     /* Read options */