[POWERPC] powermac: Use generic suspend code

This adds platform_suspend_ops for PMU based machines, directly in
the PMU driver.  This allows suspending via /sys/power/state
on powerbooks.

The patch also replaces the PMU ioctl with a simple call to
pm_suspend(PM_SUSPEND_MEM).

Additionally, it cleans up some debug code.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>