optee: fix invalid of_node_put() in optee_driver_init()

The first node supplied to of_find_matching_node() has its reference
counter decreased as part of call to that function. In optee_driver_init()
after calling of_find_matching_node() it's invalid to call of_node_put() on
the supplied node again.

So remove the invalid call to of_node_put().

Reported-by: Alex Shi <alex.shi@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>