arm64: dts: ti: k3-j721e-main: fix RNG node clock id

The RNG node for this platform claims pka_in_clk. Change it to claim the
correct clock x1_clk. [1]

[1]: https://downloads.ti.com/tisci/esd/latest/5_soc_doc/j721e/clocks.html#clocks-for-sa2-ul0-device



Signed-off-by: Daniel Parks <danielrparks@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Jayesh Choudhary <j-choudhary@ti.com>
Link: https://lore.kernel.org/r/f29e2c65dc7310a926af8a676651592afac04b03.1659981162.git.danielrparks@ti.com