clk: versal: Fix watchdog clock issue

Enable mux based clocks to populate LPD_LSBUS clock to xilinx_wwdt
driver. Skip reading clock rate for the mux based clocks with
parent clock id is zero.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>