xsk: add missing virtual address conversion for page

In commit 7ead440 ("xsk: convert xdp_copy_frags_from_zc() to use
page_pool_dev_alloc()"), when converting from netmem to page, I missed a
call to page_address() around skb_frag_page(frag) to get the virtual
address of the page. This commit uses skb_frag_address() helper to fix
the issue.

Fixes: 7ead440 ("xsk: convert xdp_copy_frags_from_zc() to use page_pool_dev_alloc()")
Reviewed-by: Alexander Lobakin <[email protected]>
Signed-off-by: Bui Quang Minh <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: minhbq-99

net/core/xdp.c

@@ -709,8 +709,7 @@ static noinline bool xdp_copy_frags_from_zc(struct sk_buff *skb,
 			return false;
 		}
 
-		memcpy(page_address(page) + offset,
-		       skb_frag_page(frag) + skb_frag_off(frag),
+		memcpy(page_address(page) + offset, skb_frag_address(frag),
 		       LARGEST_ALIGN(len));
 		__skb_fill_page_desc_noacc(sinfo, i, page, offset, len);