[DRIVERS] clk: Clocking APIs to show summary and tree

Linux already provides mechanism to show summary of clock tree and
also dump it via debugfs.

This patch provides APIs for linux-like clock tree summary and
clock tree dump.

Signed-off-by: Jimmy Durand Wesolowski <jimmy.durand-wesolowski@openwide.fr>
[ARM] Add imx6 specific command

This patch adds imx6 specific command for debugging purpose.

Signed-off-by: Jimmy Durand Wesolowski <jimmy.durand-wesolowski@openwide.fr>