zynqmp: pm: Correct WDT clock database

WDT used by APU is FPD_WDT. FPD WDT clock is controlled by
FPD_SLCR.WDT_CLK_SEL register. Correct the same in WDT clock
database.

As per FPD_SLCR.WDT_CLK_SEL register, there can be only two
parents of WDT clock not three. Fix the same by correcting it's
parents in clock database.

Signed-off-by: Tejas Patel <tejas.patel@xilinx.com>
Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Acked-by: Jolly Shah <jolly.shah@xilinx.com>