Hi Rajesh,
The warning informs you that the SPLL_CLK frequency must be between 90 MHz and 160 MHz.
So, I recommend you to set the SPLL_CLK = 160 MHz and for SYS_CLK set SPLL_CLK/2. After that, you reach SYS_CLK = 80 MHz without warnings.

I hope it helps you.
If you have any questions, let me know.
Best Regards,
Diana