x86/xen: add FRAME_END to xen_hypercall_hvm()

xen_hypercall_hvm() is missing a FRAME_END at the end, add it.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202502030848.HTNTTuo9-lkp@intel.com/


Fixes: b4845bb6 ("x86/xen: add central hypercall functions")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>