xen: remove unnecessary (void*) conversions

Pointer variables of void * type do not require type cast.

Signed-off-by: Yu Zhe <yuzhe@nfschina.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20230316083954.4223-1-yuzhe@nfschina.com


Signed-off-by: Juergen Gross <jgross@suse.com>