NFC: pn533: bound the UART receive buffer

In the Linux kernel, the following vulnerability has been resolved:

NFC: pn533: bound the UART receive buffer

pn532_receive_buf() appends every incoming byte to dev->recv_skb and

only resets the buffer after pn532_uart_rx_is_frame() recognizes a

complete frame. A continuous stream of bytes without a valid PN532 frame

header therefore keeps growing the skb until skb_put_u8() hits the tail

limit.

Drop the accumulated partial frame once the fixed receive buffer is full

so malformed UART traffic cannot grow the skb past

PN532_UART_SKB_BUFF_LEN.