[patch][lra] Comment typo fix

[Steven Bosscher]

I suppose no-one would object if I commit this as obvious at some point?

Index: lra-constraints.c
===================================================================
--- lra-constraints.c   (revision 191858)
+++ lra-constraints.c   (working copy)
@@ -4293,7 +4293,7 @@ update_ebb_live_info (rtx head, rtx tail
        {
          if (prev_bb != NULL)
            {
-             /* Udpate DF_LR_IN (prev_bb):  */
+             /* Update DF_LR_IN (prev_bb):  */
              EXECUTE_IF_SET_IN_BITMAP (&check_only_regs, 0, j, bi)
                if (bitmap_bit_p (&live_regs, j))
                  bitmap_set_bit (DF_LR_IN (prev_bb), j);