netfs: Pass a pointer to virt_to_page()

Like the other calls in this function virt_to_page() expects
a pointer, not an integer.

However since many architectures implement virt_to_pfn() as
a macro, this function becomes polymorphic and accepts both a
(unsigned long) and a (void *).

Fix this up with an explicit cast.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

fs/netfs/iterator.c

@@ -240,7 +240,7 @@ static ssize_t netfs_extract_kvec_to_sg(struct iov_iter *iter,
 			if (is_vmalloc_or_module_addr((void *)kaddr))
 				page = vmalloc_to_page((void *)kaddr);
 			else
-				page = virt_to_page(kaddr);
+				page = virt_to_page((void *)kaddr);
 
 			sg_set_page(sg, page, len, off);
 			sgtable->nents++;