i965/fs: Abort on unsupported opcodes rather than failing.

Final code generation should never fail.  This is a bug, and there
should be no user-triggerable cases where this could occur.

Also, we're not going to have a fail() method in a moment.

v2: Just abort() rather than assert, to cover the NDEBUG case
    (suggested by Eric).

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Paul Berry <stereotype441@gmail.com>

src/mesa/drivers/dri/i965/brw_fs_emit.cpp

@@ -1012,7 +1012,7 @@ fs_visitor::generate_code()
 	 } else {
 	    _mesa_problem(ctx, "Unsupported opcode %d in FS", inst->opcode);
 	 }
-	 fail("unsupported opcode in FS\n");
+	 abort();
       }
 
       if (unlikely(INTEL_DEBUG & DEBUG_WM)) {