mm: mm_event: remove get/put_online_cpus call

remove get/put_online_cpus call since it could cause
deadlock in cpu hotplug path. This might cause race
but should be rare and we should be able to correct
that with the next dump.

=======================================================
    Task name: Binder:897_2 pid: 3255 cpu: 0 start: 0xffffffd39e2f5700
    state: 0x2 exit_state: 0x0 stack base: 0xffffff80241f0000 Prio: 116
    Stack:
    [<ffffff9048f3163c>] __switch_to.cfi+0x138
    [<ffffff904a947808>] __schedule+0xb7c
    [<ffffff904a94dbdc>] rwsem_down_read_failed.cfi+0x270
    [<ffffff904900a0a4>] __percpu_down_read.cfi+0x164
    [<ffffff90491bc4e8>] record_stat+0x6c0
    [<ffffff90491bbdfc>] mm_event_end.cfi+0x14c
    [<ffffff904916c280>] try_to_free_pages.cfi+0xaf4
    [<ffffff904914a598>] __alloc_pages_nodemask.cfi+0x9c8
    [<ffffff9049aa6350>] zcomp_cpu_up_prepare.cfi+0x88
    [<ffffff9048f66da8>] cpuhp_invoke_callback+0x378
    [<ffffff9048f664e0>] _cpu_up+0x1bc
    [<ffffff9048f6aadc>] enable_nonboot_cpus.cfi+0x208
    [<ffffff90490135f4>] suspend_devices_and_enter.cfi+0xc20
    [<ffffff9049012844>] pm_suspend.cfi+0xb30
    [<ffffff9049010568>] state_store.cfi+0x94
    [<ffffff904a9339dc>] kobj_attr_store.cfi+0x34
    [<ffffff90492ed9ec>] sysfs_kf_write.cfi+0x64
    [<ffffff90492eb51c>] kernfs_fop_write.cfi+0x1a4
    [<ffffff90491fbf34>] __vfs_write.cfi+0x50
    [<ffffff90491fbd58>] vfs_write.cfi+0xcc
    [<ffffff90491fefd4>] SyS_write.cfi+0xa4
    [<ffffff9048e84080>] el0_svc_naked+0x34

Test: manual suspend/resume test
Bug: 132011965
Change-Id: I112ca0d25e825bb4e0e8979d9b4f1d8e6090147f
Signed-off-by: Martin Liu <liumartin@google.com>
(cherry picked from commit 5f419093)