Trivial Typo's in bier comments/docs.

Change-Id: I3b3e868277d5caf6b1341814003a3bc5726c2df9
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>
diff --git a/src/vnet/bier/bier_entry.h b/src/vnet/bier/bier_entry.h
index 629e47a..afa90ab 100644
--- a/src/vnet/bier/bier_entry.h
+++ b/src/vnet/bier/bier_entry.h
@@ -16,7 +16,7 @@
  * bier_entry : The BIER entry
  *
  * The interface to the BIER entry is through a bier_entry_t* rather
- * than an index. This is becuase the BIER table allocates the entries
+ * than an index. This is because the BIER table allocates the entries
  * in a contiguous array once and only once when the table is created.
  * this is done for forwarding performance. The entry is thus not subject
  * to realloc, and does not need to be malloc'd when a route to that