tee: optee: Fix supplicant wait loop

tee: optee: Fix supplicant wait loop

OP-TEE supplicant is a user-space daemon and it's possible for it
be hung or crashed or killed in the middle of processing an OP-TEE
RPC call. It becomes more complicated when there is incorrect shutdown
ordering of the supplicant process vs the OP-TEE client application which
can eventually lead to system hang-up waiting for the closure of the
client application.

Allow the client process waiting in kernel for supplicant response to
be killed rather than indefinitely waiting in an unkillable state. Also,
a normal uninterruptible wait should not have resulted in the hung-task
watchdog getting triggered, but the endless loop would.

This fixes issues observed during system reboot/shutdown when supplicant
got hung for some reason or gets crashed/killed which lead to client
getting hung in an unkillable state. It in turn lead to system being in
hung up state requiring hard power off/on to recover.

Fixes: 4fb0a5eb364d ("tee: add OP-TEE driver")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Cc: stable@vger.kernel.org
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>