bhyve: do not hold CRB mutex when executing TPM commands

[corvink]

Summary

TPM commands can take up to several seconds to execute. If we hold the
CRB mutex while executing the command, MMIO accesses could be blocked
for a long time. Therefore, just copy all required values and work on
the copied values.

[markj]

usr.sbin/bhyve/tpm_intf_crb.c

219

Now it's possible for the thread to miss wakeups. Suppose the thread is processing a command, and tpm_crb_deinit() is called while the lock is dropped. The thread will reacquire the lock and go to sleep without checking crb->closing.

[corvink]

• fix race on thread signalling