net: strparser: fix skb_head leak in strp_abort_strp()

In the Linux kernel, the following vulnerability has been resolved: net: strparser: fix skb_head leak in strp_abort_strp() When the stream parser is aborted, for example after a message assembly timeout, it can still hold a reference to a partially assembled message in strp->skb_head. That skb is not released in strp_abort_strp(), which leaks the partially assembled message and can be triggered repeatedly to exhaust memory. Fix this by freeing strp->skb_head and resetting the parser state in the abort path. Leave strp_stop() unchanged so final cleanup still happens in strp_done() after the work and timer have been synchronized.