vsock/virtio: fix "comparison of distinct pointer types lacks a cast" warning

After backporting commit 581512a6 ("vsock/virtio: MSG_ZEROCOPY
flag support") in CentOS Stream 9, CI reported the following error:

    In file included from ./include/linux/kernel.h:17,
                     from ./include/linux/list.h:9,
                     from ./include/linux/preempt.h:11,
                     from ./include/linux/spinlock.h:56,
                     from net/vmw_vsock/virtio_transport_common.c:9:
    net/vmw_vsock/virtio_transport_common.c: In function ‘virtio_transport_can_zcopy‘:
    ./include/linux/minmax.h:20:35: error: comparison of distinct pointer types lacks a cast [-Werror]
       20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
          |                                   ^~
    ./include/linux/minmax.h:26:18: note: in expansion of macro ‘__typecheck‘
       26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
          |                  ^~~~~~~~~~~
    ./include/linux/minmax.h:36:31: note: in expansion of macro ‘__safe_cmp‘
       36 |         __builtin_choose_expr(__safe_cmp(x, y), \
          |                               ^~~~~~~~~~
    ./include/linux/minmax.h:45:25: note: in expansion of macro ‘__careful_cmp‘
       45 | #define min(x, y)       __careful_cmp(x, y, <)
          |                         ^~~~~~~~~~~~~
    net/vmw_vsock/virtio_transport_common.c:63:37: note: in expansion of macro ‘min‘
       63 |                 int pages_to_send = min(pages_in_iov, MAX_SKB_FRAGS);

We could solve it by using min_t(), but this operation seems entirely
unnecessary, because we also pass MAX_SKB_FRAGS to iov_iter_npages(),
which performs almost the same check, returning at most MAX_SKB_FRAGS
elements. So, let's eliminate this unnecessary comparison.

Fixes: 581512a6 ("vsock/virtio: MSG_ZEROCOPY flag support")
Cc: avkrasnov@salutedevices.com
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Arseniy Krasnov <avkrasnov@salutedevices.com>
Link: https://lore.kernel.org/r/20231206164143.281107-1-sgarzare@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/vmw_vsock/virtio_transport_common.c

@@ -59,8 +59,7 @@ static bool virtio_transport_can_zcopy(const struct virtio_transport *t_ops,
 	t_ops = virtio_transport_get_ops(info->vsk);
 
 	if (t_ops->can_msgzerocopy) {
-		int pages_in_iov = iov_iter_npages(iov_iter, MAX_SKB_FRAGS);
-		int pages_to_send = min(pages_in_iov, MAX_SKB_FRAGS);
+		int pages_to_send = iov_iter_npages(iov_iter, MAX_SKB_FRAGS);
 
 		/* +1 is for packet header. */
 		return t_ops->can_msgzerocopy(pages_to_send + 1);