tee: optee: Fix missing devices unregister during optee_remove

tee: optee: Fix missing devices unregister during optee_remove

commit 11b6d89c3593571860747aa593d89eb972f4be5d upstream.

When OP-TEE driver is built as a module, OP-TEE client devices
registered on TEE bus during probe should be unregistered during
optee_remove. So implement optee_unregister_devices() accordingly.

Fixes: a8611d81269b ("tee: optee: add TEE bus device enumeration support")
Reported-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
[SG: backport to 5.4, dev name s/optee-ta/optee-clnt/]
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>