i965: Fix a bug in i965 compute-to-MRF.

Fixes piglit glsl-fs-texture2d-branching.  I couldn't come up with a
testcase that didn't involve dead code, but it's still worthwhile to
fix I think.

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

@@ -3170,6 +3170,7 @@ fs_visitor::compute_to_mrf()
 	  */
 	 if (scan_inst->opcode == BRW_OPCODE_DO ||
 	     scan_inst->opcode == BRW_OPCODE_WHILE ||
+	     scan_inst->opcode == BRW_OPCODE_ELSE ||
 	     scan_inst->opcode == BRW_OPCODE_ENDIF) {
 	    break;
 	 }