xen: Convert kmap() to kmap_local_page()

kmap() is being deprecated and these usages are all local to the thread
so there is no reason kmap_local_page() can't be used.

Replace kmap() calls with kmap_local_page().
Signed-off-by: NAlaa Mohamed <eng.alaamohamedsoliman.am@gmail.com>
Reviewed-by: NJuergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220419234328.10346-1-eng.alaamohamedsoliman.am@gmail.comSigned-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>

drivers/xen/gntalloc.c

@@ -178,9 +178,9 @@ static void __del_gref(struct gntalloc_gref *gref)
 	unsigned long addr;
 
 	if (gref->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
-		uint8_t *tmp = kmap(gref->page);
+		uint8_t *tmp = kmap_local_page(gref->page);
 		tmp[gref->notify.pgoff] = 0;
-		kunmap(gref->page);
+		kunmap_local(tmp);
 	}
 	if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
 		notify_remote_via_evtchn(gref->notify.event);