pml/yalla: fix getting size of a continuous type.

pull request #3765 introduced a bug where the extent of a type is used
instead of its size.

Signed-off-by: Yossi Itigin <yosefe@mellanox.com>

ompi/mca/pml/yalla/pml_yalla_datatype.h

@@ -27,10 +27,11 @@ OBJ_CLASS_DECLARATION(mca_pml_yalla_convertor_t);
 #define PML_YALLA_INIT_MXM_REQ_DATA(_req_base, _buf, _count, _dtype, _stream_type, ...) \
     { \
         size_t size; \
-        ptrdiff_t lb; \
+        ptrdiff_t lb, extent; \
         \
         if (opal_datatype_is_contiguous_memory_layout(&(_dtype)->super, _count)) { \
-            ompi_datatype_get_true_extent(_dtype, &lb, &size); \
+            ompi_datatype_get_true_extent(_dtype, &lb, &extent); \
+            ompi_datatype_type_size(_dtype, &size); \
             (_req_base)->data_type          = MXM_REQ_DATA_BUFFER; \
             (_req_base)->data.buffer.ptr    = (char *)_buf + lb; \
             (_req_base)->data.buffer.length = size * (_count); \