x86/shadow: fix PAE check for top-level table unshadowing

x86/shadow: fix PAE check for top-level table unshadowing

Clearly within the for_each_vcpu() the vCPU of this loop is meant, not
the (loop invariant) one the fault occurred on.

Fixes: 3d5e6a3ff383 ("x86 hvm: implement HVMOP_pagetable_dying")
Fixes: ef3b0d8d2c39 ("x86/shadow: shadow_table[] needs only one entry for PV-only configs")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: f8fdceefbb1193ec81667eb40b83bc525cb71204
master date: 2023-01-20 09:23:42 +0100