nfc: pn533: Clear nfc_target before being used

Fix a slab-out-of-bounds read that occurs in nla_put() called from
nfc_genl_send_target() when target->sensb_res_len, which is duplicated
from an nfc_target in pn533, is too large as the nfc_target is not
properly initialized and retains garbage values. Clear nfc_targets with
memset() before they are used.

Found by a modified version of syzkaller.

BUG: KASAN: slab-out-of-bounds in nla_put
Call Trace:
 memcpy
 nla_put
 nfc_genl_dump_targets
 genl_lock_dumpit
 netlink_dump
 __netlink_dump_start
 genl_family_rcv_msg_dumpit
 genl_rcv_msg
 netlink_rcv_skb
 genl_rcv
 netlink_unicast
 netlink_sendmsg
 sock_sendmsg
 ____sys_sendmsg
 ___sys_sendmsg
 __sys_sendmsg
 do_syscall_64

Fixes: 673088fb ("NFC: pn533: Send ATR_REQ directly for active device detection")
Fixes: 361f3cb7

 ("NFC: DEP link hook implementation for pn533")
Signed-off-by: Minsuk Kang <linuxlovemin@yonsei.ac.kr>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221214015139.119673-1-linuxlovemin@yonsei.ac.kr
Signed-off-by: Jakub Kicinski <kuba@kernel.org>