glsl: Just access the ir_expression_operation strings table directly

The operator_string functions gave us some protection against a
malformed table.  Now that the table is generated from the same data
that generates the enum, this is not a concern.  Just cut out the middle
man.

   text	   data	    bss	    dec	    hex	filename
7531892	 273992	  28584	7834468	 778b64	i965_dri-64bit-before.so
7531828	 273992	  28584	7834404	 778b24	i965_dri-64bit-after.so

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

src/compiler/glsl/ir.h

@@ -1363,6 +1363,8 @@ public:
 
 #include "ir_expression_operation.h"
 
+extern const char *const ir_expression_operation_strings[ir_last_opcode + 1];
+
 class ir_expression : public ir_rvalue {
 public:
    ir_expression(int op, const struct glsl_type *type,
@@ -1429,17 +1431,6 @@ public:
              operation == ir_quadop_vector;
    }
 
-   /**
-    * Return a string representing this expression's operator.
-    */
-   const char *operator_string();
-
-   /**
-    * Return a string representing this expression's operator.
-    */
-   static const char *operator_string(ir_expression_operation);
-
-
    /**
     * Do a reverse-lookup to translate the given string into an operator.
     */