Fix MIPS --enable-werror build

[Richard Sandiford]

As per subject.  Tested on mips64-elf and mipsisa64-elf.  Applied.

Richard


gcc/
        * config/mips/mips.c (mips_process_sync_loop): Add missing
        enum cast.

Index: gcc/config/mips/mips.c
===================================================================
--- gcc/config/mips/mips.c      2012-06-23 21:41:21.000000000 +0100
+++ gcc/config/mips/mips.c      2012-06-23 21:41:22.065523986 +0100
@@ -12048,7 +12048,7 @@ #define READ_OPERAND(WHAT, DEFAULT) \
       model = MEMMODEL_ACQUIRE;
       break;
     default:
-      model = INTVAL (operands[memmodel_attr]);
+      model = (enum memmodel) INTVAL (operands[memmodel_attr]);
     }
 
   mips_multi_start ();