Remove fake platform device used for PM init.  Move pdata values which
are common across all current platforms into pm.c.

Also, since PM is only used on da8xx, remove davinci_pm_init() from
common init code, and only use in da850/omapl138 board files that are
currently creating the fake platform_device.
Suggested-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
[nsekhar@ti.com: subject line adjustment]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>