[XEN][POWERPC] The VIO rewrite

[XEN][POWERPC] The VIO rewrite
Once you figure it all out, its time to do a rewrite, lots of code I
thougth I needed is now removed and less PPC specific code now exists.
This patch uses the MEMORY_HOTPLUG system to add a region to the
Kernel Linear Mapping that will be used exclusively to map in
Granted/Foreign pages.  This creates "struct page" objects in Linux
which are necessary to perform VIO operations.  When one of these
pages are grant_mapped the pfn2mfn() translation in Xen is updated to
reflect the association and the subsequent H_ENTER() from the domain
will contain the correct mapping.
Signed-off-by: Jimi Xenidis <jimix@watson.ibm.com>
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>