ARM: tegra: cpufreq: Adjust memory frequency with cpu frequency

Adjusts the minimum memory frequency when the cpu frequency
changes.  The values are currently hardcoded to a reasonable
default.  If memory frequency scaling is not enabled this
patch will have no effect.

Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Colin Cross <ccross@android.com>