optee: Suppress false positive kmemleak report in optee_handle_rpc()

We observed the following kmemleak report:
unreferenced object 0xffff000007904500 (size 128):
  comm "swapper/0", pid 1, jiffies 4294892671 (age 44.036s)
  hex dump (first 32 bytes):
    00 47 90 07 00 00 ff ff 60 00 c0 ff 00 00 00 00  .G......`.......
    60 00 80 13 00 80 ff ff a0 00 00 00 00 00 00 00  `...............
  backtrace:
    [<000000004c12b1c7>] kmem_cache_alloc+0x1ac/0x2f4
    [<000000005d23eb4f>] tee_shm_alloc+0x78/0x230
    [<00000000794dd22c>] optee_handle_rpc+0x60/0x6f0
    [<00000000d9f7c52d>] optee_do_call_with_arg+0x17c/0x1dc
    [<00000000c35884da>] optee_open_session+0x128/0x1ec
    [<000000001748f2ff>] tee_client_open_session+0x28/0x40
    [<00000000aecb5389>] optee_enumerate_devices+0x84/0x2a0
    [<000000003df18bf1>] optee_probe+0x674/0x6cc
    [<000000003a4a534a>] platform_drv_probe+0x54/0xb0
    [<000000000c51ce7d>] really_probe+0xe4/0x4d0
    [<000000002f04c865>] driver_probe_device+0x58/0xc0
    [<00000000b485397d>] device_driver_attach+0xc0/0xd0
    [<00000000c835f0df>] __driver_attach+0x84/0x124
    [<000000008e5a429c>] bus_for_each_dev+0x70/0xc0
    [<000000001735e8a8>] driver_attach+0x24/0x30
    [<000000006d94b04f>] bus_add_driver+0x104/0x1ec

This is not a memory leak because we pass the share memory pointer
to secure world and would get it from secure world before releasing it.

Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>