[wide-int] Fix UNSIGNED_FIX typo

[Richard Sandiford]

"t" had got switched to "x" during the conversion.  This showed up in
one of the alpha g++.dg tests.

Applied as obvious.

Richard


Index: gcc/simplify-rtx.c
===================================================================
--- gcc/simplify-rtx.c	2013-11-03 13:01:39.083385620 +0000
+++ gcc/simplify-rtx.c	2013-11-03 20:22:41.115469359 +0000
@@ -1819,7 +1819,8 @@ simplify_const_unary_operation (enum rtx
 	  if (REAL_VALUES_LESS (t, x))
 	    return immed_wide_int_const (wmax, mode);
 
-	  return immed_wide_int_const (real_to_integer (&t, &fail, width), mode);
+	  return immed_wide_int_const (real_to_integer (&x, &fail, width),
+				       mode);
 	  break;
 
 	default: