net: usb: cdc-phonet: fix skb frags[] overflow in rx_complete()

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

net: usb: cdc-phonet: fix skb frags[] overflow in rx_complete()

A malicious USB device claiming to be a CDC Phonet modem can overflow

the skb_shared_info->frags[] array by sending an unbounded sequence of

full-page bulk transfers.

Drop the skb and increment the length error when the frag limit is

reached. This matches the same fix that commit f0813bcd2d9d ("net:

wwan: t7xx: fix potential skb->frags overflow in RX path") did for the

t7xx driver.