firewire: core: fix race condition against transaction list

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

firewire: core: fix race condition against transaction list

The list of transaction is enumerated without acquiring card lock when processing AR response event. This causes a race condition bug when processing AT request completion event concurrently.

This commit fixes the bug by put timer start for split transaction expiration into the scope of lock. The value of jiffies in card structure is referred before acquiring the lock.