physmem coverity issues

Change-Id: Ie9ff9b751190632dfc4576e5cbb1987a4142af5e
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vlib/buffer.c b/src/vlib/buffer.c
index 2f15e65..22cf799 100644
--- a/src/vlib/buffer.c
+++ b/src/vlib/buffer.c
@@ -860,7 +860,7 @@
   vlib_buffer_pool_t *p;
   vlib_physmem_map_t *m = vlib_physmem_get_map (vm, physmem_map_index);
   uword start = pointer_to_uword (m->base);
-  uword size = m->n_pages << m->log2_page_size;
+  uword size = (uword) m->n_pages << m->log2_page_size;
 
   if (bm->buffer_mem_size == 0)
     {