tee: fix memory leak in tee_dyn_shm_alloc_helper

When shm_register() fails in tee_dyn_shm_alloc_helper(), the pre-allocated
pages array is not freed, resulting in a memory leak.

Fixes: cf444150 ("tee: optee: Move pool_op helper functions")
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>