n1sdp: add frequency lookup table for n1sdp_pll

This patch adds lookup table for frequencies that are not an
integer multiplication of the reference clock.
In such case, n1sdp_pll module sees if a matching frequency is
available in lookup table and uses PLL parameters from the table.

Change-Id: Ic737b3bed17190425064a37a05de5cf35f84dffb
Signed-off-by: Manoj Kumar <manoj.kumar3@arm.com>