[POWERPC] pseries: phyp dump: Invalidate and print dump areas

This adds routines to
a. invalidate dump
b. calculate region that is reserved and needs to be freed.  This is
   exported through sysfs interface.

Unregister has been removed for now as it wasn't being used.

Signed-off-by: Manish Ahuja <mahuja@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>