buffers: add compile-time option to set buffer alignment

Type: improvement
Change-Id: I88c4c45bed0bdd8686e17e4f77a7d32a08c995aa
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vlib/buffer.c b/src/vlib/buffer.c
index 005326d..82fe641 100644
--- a/src/vlib/buffer.c
+++ b/src/vlib/buffer.c
@@ -471,11 +471,7 @@
 vlib_buffer_alloc_size (uword ext_hdr_size, uword data_size)
 {
   uword alloc_size = ext_hdr_size + sizeof (vlib_buffer_t) + data_size;
-  alloc_size = CLIB_CACHE_LINE_ROUND (alloc_size);
-
-  /* in case when we have even number of cachelines, we add one more for
-   * better cache occupancy */
-  alloc_size |= CLIB_CACHE_LINE_BYTES;
+  alloc_size = round_pow2 (alloc_size, VLIB_BUFFER_ALIGN);
 
   return alloc_size;
 }