NFC: fix attrs checks in netlink interface

commit 18917d51472fe3b126a3a8f756c6b18085eb8130 upstream.

nfc_genl_deactivate_target() relies on the NFC_ATTR_TARGET_INDEX
attribute being present, but doesn't check whether it is actually
provided by the user. Same goes for nfc_genl_fw_download() and
NFC_ATTR_FIRMWARE_NAME.

This patch adds appropriate checks.

Found with syzkaller.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>