arch: powerpc: update the IFC IP input clock

arch: powerpc: update the IFC IP input clock

IFC IP clock is always a constant divisor of platform clock
pre-defined per SoC. Clock control register (CCR) used in
current implementation governs IFC IP output clock.

Update sys_info->freq_localbus to represent IFC input clock with
value constant divisor of platform clock.

Signed-off-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>