libxc/restore: Fix data auditing in handle_x86_pv_info()

libxc/restore: Fix data auditing in handle_x86_pv_info()

handle_x86_pv_info() has a subtle bug.  It uses an 'else if' chain with a
clause in the middle which doesn't exit unconditionally.  In practice, this
means that when restoring a 32bit PV guest, later sanity checks are skipped.

Rework the logic a little to be simpler.  There are exactly two valid
combinations of fields in X86_PV_INFO, so factor this out and check them all
in one go, before making adjustments to the current domain.

Once adjustments have been completed successfully, sanity check the result
against the X86_PV_INFO settings in one go, rather than piece-wise.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Ian Jackson <ian.jackson@eu.citrix.com>