skb should be free in virtual_nci_send(), otherwise kmemleak will report
memleak.

Steps for reproduction (simulated in qemu):
	cd tools/testing/selftests/nci
	make
	./nci_dev

BUG: memory leak
unreferenced object 0xffff888107588000 (size 208):
  comm "nci_dev", pid 206, jiffies 4294945376 (age 368.248s)
  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:
    [<000000008d94c8fd>] __alloc_skb+0x1da/0x290
    [<00000000278bc7f8>] nci_send_cmd+0xa3/0x350
    [<0000000081256a22>] nci_reset_req+0x6b/0xa0
    [<000000009e721112>] __nci_request+0x90/0x250
    [<000000005d556e59>] nci_dev_up+0x217/0x5b0
    [<00000000e618ce62>] nfc_dev_up+0x114/0x220
    [<00000000981e226b>] nfc_genl_dev_up+0x94/0xe0
    [<000000009bb03517>] genl_family_rcv_msg_doit.isra.14+0x228/0x2d0
    [<00000000b7f8c101>] genl_rcv_msg+0x35c/0x640
    [<00000000c94075ff>] netlink_rcv_skb+0x11e/0x350
    [<00000000440cfb1e>] genl_rcv+0x24/0x40
    [<0000000062593b40>] netlink_unicast+0x43f/0x640
    [<000000001d0b13cc>] netlink_sendmsg+0x73a/0xbf0
    [<000000003272487f>] __sys_sendto+0x324/0x370
    [<00000000ef9f1747>] __x64_sys_sendto+0xdd/0x1b0
    [<000000001e437841>] do_syscall_64+0x3f/0x90

Fixes: e624e6c3 ("nfc: Add a virtual nci device driver")
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221020030505.15572-1-shangxiaojing@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>