I was incorrect about CPOL. CPOL =1 for AFE5801. Please refer to either pg. 25 (read), pg. 20 (write) of AFE5801 datasheet. CPOL (Clock Polarity)= 1 since SCLK starts high and falling edge is the first edge of transmission.
CPHA is either 0 or 1, not sure. Mode 3 (CPOL=1, CPHA=1) also works in my program.
Hopefully, someone benefits
Thanks,
Mohit Kapur