msm: platsmp: Set boot address in smp_prepare_cpus() stage

Set the cold boot address for CPUs in the smp_prepare_cpus()
stage instead of during the hotplug phase to avoid multiple
calls to the secure monitor for each CPU. Also, remove cpus from
the present mask if they don't have a supported cold boot flag.
This way hotplug can't fail for those CPUs because they were
never allowed to be hotplugged to begin with.

While we're here also mark the coldboot flags array as
__initdata to save a few bytes after kernel init

Change-Id: I96ed64cb21da21b732488060dc7bb8d957f8d646
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>