ARM: tegra: clock: Convert global lock to a lock per clock

Give each clock its own lock, and remove all lock traversals from
parent to child clocks to prevent AB-BA deadlocks.

This brings the locking in line with the common struct clk
patches and should make conversion simple.

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