x86/xen: Fix sparse warning in enlighten_pv.c

x86/xen: Fix sparse warning in enlighten_pv.c

The sparse tool issues a warning for arch/x76/xen/enlighten_pv.c:

   arch/x86/xen/enlighten_pv.c:120:9: sparse: sparse: incorrect type
     in initializer (different address spaces)
     expected void const [noderef] __percpu *__vpp_verify
     got bool *

This is due to the percpu variable xen_in_preemptible_hcall being
exported via EXPORT_SYMBOL_GPL() instead of EXPORT_PER_CPU_SYMBOL_GPL().

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512140856.Ic6FetG6-lkp@intel.com/
Fixes: fdfd811ddde3 ("x86/xen: allow privcmd hypercalls to be preempted")
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20251215115112.15072-1-jgross@suse.com>