i965/cs: Return 1 for regs_read on CS_OPCODE_CS_TERMINATE

This prevents an assertion failure in brw_fs_live_variables.cpp,
fs_live_variables::setup_one_read: Assertion `var < num_vars' failed.

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>

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

@@ -698,6 +698,9 @@ fs_inst::regs_read(int arg) const
          return 1;
       break;
 
+   case CS_OPCODE_CS_TERMINATE:
+      return 1;
+
    default:
       if (is_tex() && arg == 0 && src[0].file == GRF)
          return mlen;