guest/pvh: fix handling of multiboot module list

guest/pvh: fix handling of multiboot module list

When booting Xen as a PVH guest the data in the PVH start info
structure is copied over to a multiboot structure and a module list
array that resides in the .init section of the Xen image. The
resulting multiboot module list is then handed to the generic boot
process using the physical address in mbi->mods_addr.

This works fine as long as the Xen image doesn't relocate itself, if
there's such a relocation the physical addresses of multiboot module
list is no longer valid.

Fix this by handing the virtual address of the module list to the
generic boot process instead of it's physical address.

Reported-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>