n1sdp: add dynamic calculations of PLL parameters

Created by: arnoldgb-arm

To find optimal pll parameter values such as fbdiv, refdiv and postdiv to achieve the closest freq to the actual rate.

Signed-off-by: Arnold Gabriel Benedict arnoldgabriel.benedict@arm.com Change-Id: I02738ca43b9ceef833306d19130245f240a482b8