sched: tune: Fix lacking spinlock initialization

sched: tune: Fix lacking spinlock initialization

The spinlock used by boost_groups in sched tune must be initialized.
This commit fixes this lack and the following errors:

[    0.384739] c2 BUG: spinlock bad magic on CPU#2, swapper/2/0
[    0.390313] c2  lock: 0xffffffc15fe1fc80, .magic:00000000, .owner: <none>/-1, .owner_cpu: 0
[    0.398739] c2 CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.4.6+ #4
[    0.404816] c2 Hardware name: Spreadtrum SP9860gBoard (DT)
[    0.410462] c2 Call trace:
[    0.413159] c2 [<ffffff800808b50c>] dump_backtrace+0x0/0x210
[    0.418803] c2 [<ffffff800808b73c>] show_stack+0x20/0x28
[    0.424100] c2 [<ffffff8008433310>] dump_stack+0xa8/0xe0
[    0.429398] c2 [<ffffff8008139398>] spin_dump+0x78/0x9c
[    0.434608] c2 [<ffffff80081393ec>] spin_bug+0x30/0x3c
[    0.439644] c2 [<ffffff80081394e4>] do_raw_spin_lock+0xac/0x1b4
[    0.445639] c2 [<ffffff8008abffe4>] _raw_spin_lock_irqsave+0x58/0x68
[    0.451977] c2 [<ffffff800812a560>] schedtune_enqueue_task+0x84/0x3bc
[    0.458320] c2 [<ffffff8008111678>] enqueue_task_fair+0x438/0x208c
[    0.464487] c2 [<ffffff80080feeec>] activate_task+0x70/0xd0
[    0.470130] c2 [<ffffff80080ff4a4>] ttwu_do_activate.constprop.131+0x4c/0x98
[    0.477079] c2 [<ffffff80081005d0>] try_to_wake_up+0x254/0x54c
[    0.482899] c2 [<ffffff80081009d4>] default_wake_function+0x30/0x3c
[    0.489154] c2 [<ffffff8008122464>] autoremove_wake_function+0x3c/0x6c
[    0.495754] c2 [<ffffff8008121b70>] __wake_up_common+0x64/0xa4
[    0.501574] c2 [<ffffff8008121e9c>] __wake_up+0x48/0x60
[    0.506788] c2 [<ffffff8008150fac>] rcu_gp_kthread_wake+0x50/0x5c
[    0.512866] c2 [<ffffff8008151fec>] note_gp_changes+0xac/0xd4
[    0.518597] c2 [<ffffff8008153044>] rcu_process_callbacks+0xe8/0x93c
[    0.524940] c2 [<ffffff80080d0b84>] __do_softirq+0x24c/0x5b8
[    0.530584] c2 [<ffffff80080d1284>] irq_exit+0xc0/0xec
[    0.535623] c2 [<ffffff8008144208>] __handle_domain_irq+0x94/0xf8
[    0.541789] c2 [<ffffff8008082554>] gic_handle_irq+0x64/0xc0

Signed-off-by: Ke Wang <ke.wang@spreadtrum.com>