smpboot: use kmemleak_not_leak for smpboot_thread_data

Kmemleak reports the following memory leak :

    [<ffffffc0002faef8>] create_object+0x140/0x274
    [<ffffffc000cc3598>] kmemleak_alloc+0x80/0xbc
    [<ffffffc0002f707c>] kmem_cache_alloc_trace+0x148/0x1d8
    [<ffffffc00024504c>] __smpboot_create_thread.part.2+0x2c/0xec
    [<ffffffc0002452b4>] smpboot_register_percpu_thread+0x90/0x118
    [<ffffffc0016067c0>] spawn_ksoftirqd+0x1c/0x30
    [<ffffffc000200824>] do_one_initcall+0xb0/0x14c
    [<ffffffc001600820>] kernel_init_freeable+0x84/0x1e0
    [<ffffffc000cc273c>] kernel_init+0x10/0xcc
    [<ffffffc000203bbc>] ret_from_fork+0xc/0x50

This memory allocated here points to smpboot_thread_data.
Data is used as an argument for this kthread.

This will be used when smpboot_thread_fn runs. Therefore,
is not a leak.

Call kmemleak_not_leak for smpboot_thread_data pointer
to ensure that kmemleak doesn't report it as a memory
leak.

Change-Id: I02b0a7debea3907b606856e069d63d7991b67cd9
Signed-off-by: Vignesh Radhakrishnan <vigneshr@codeaurora.org>