MLK-12733: ARM: imx: imx6q: lppdr2 fix audio freq mode

MLK-12733: ARM: imx: imx6q: lppdr2 fix audio freq mode

Fix Audio frequency operation mode (100Mhz), wrong branch
condition was causing to switch to high speed timings settings
if (freq mode <= 100Mhz) use low speed timings settings

On Audio freq mode request
1. Set timings to operate on low speed
2. Switch mmdc clock root to 100Mhz

Signed-off-by: Adrian Alonso <adrian.alonso@nxp.com>
Signed-off-by: Ranjani Vaidyanathan <ranjani.vaidyanathan@nxp.com>
(cherry-picked from commit 79756d9defae46b67cd37807b859b52e63b18496)