Document CEUSEDMUX, SRUSEDMUX muxes
0: always on1: controlledCLB.SLICE_X0.CEUSEDMUX 00_39CLB.SLICE_X1.CEUSEDMUX <0 candidates>
(How used when SR?)0: never reset1: controlledCLB.SLICE_X0.SRUSEDMUX 00_35CLB.SLICE_X1.SRUSEDMUX <0 candidates>