ARM: OMAP: Merge PM code from N800 tree

ARM: OMAP: Merge PM code from N800 tree

This patch merges omap2 PM code from N800 tree.

Patch adds support for sleep while idle for omap2
and handy serial console debbugging code. It also
moves code from pm-domain.c to pm.c.

This code can be used as a base for developing
power management for all omap24xx boards.

Signed-off-by: Kai Svahn <kai.svahn@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>