NFC: nci: fix memory leak in nci_rx_data_packet()

NFC: nci: fix memory leak in nci_rx_data_packet()

Syzbot reported a memory leak about skb:

unreferenced object 0xffff88810e144e00 (size 240):
  comm "syz-executor284", pid 3701, jiffies 4294952403 (age 12.620s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff83ab79a9>] __alloc_skb+0x1f9/0x270 net/core/skbuff.c:497
    [<ffffffff82a5cf64>] alloc_skb include/linux/skbuff.h:1267 [inline]
    [<ffffffff82a5cf64>] virtual_ncidev_write+0x24/0xe0 drivers/nfc/virtual_ncidev.c:116
    [<ffffffff815f6503>] do_loop_readv_writev fs/read_write.c:759 [inline]
    [<ffffffff815f6503>] do_loop_readv_writev fs/read_write.c:743 [inline]
    [<ffffffff815f6503>] do_iter_write+0x253/0x300 fs/read_write.c:863
    [<ffffffff815f66ed>] vfs_writev+0xdd/0x240 fs/read_write.c:934
    [<ffffffff815f68f6>] do_writev+0xa6/0x1c0 fs/read_write.c:977
    [<ffffffff848802d5>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    [<ffffffff848802d5>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
    [<ffffffff84a00087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

In nci_rx_data_packet(), if we don't get a valid conn_info, we will return
directly but forget to release the skb.

Reported-by: syzbot+cdb9a427d1bc08815104@syzkaller.appspotmail.com
Fixes: 4aeee6871e8c ("NFC: nci: Add dynamic logical connections support")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Link: https://lore.kernel.org/r/20221118082419.239475-1-liushixin2@huawei.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>