coresight: trbe: remove cpuhp instance node before remove cpuhp state

cpuhp_state_add_instance() and cpuhp_state_remove_instance() should
be used in pairs. Or there will lead to the warn on
cpuhp_remove_multi_state() since the cpuhp_step list is not empty.

The following is the error log with 'rmmod coresight-trbe':
Error: Removing state 215 which has instances left.
Call trace:
  __cpuhp_remove_state_cpuslocked+0x144/0x160
  __cpuhp_remove_state+0xac/0x100
  arm_trbe_device_remove+0x2c/0x60 [coresight_trbe]
  platform_remove+0x34/0x70
  device_remove+0x54/0x90
  device_release_driver_internal+0x1e4/0x250
  driver_detach+0x5c/0xb0
  bus_remove_driver+0x64/0xc0
  driver_unregister+0x3c/0x70
  platform_driver_unregister+0x20/0x30
  arm_trbe_exit+0x1c/0x658 [coresight_trbe]
  __arm64_sys_delete_module+0x1ac/0x24c
  invoke_syscall+0x50/0x120
  el0_svc_common.constprop.0+0x58/0x1a0
  do_el0_svc+0x38/0xd0
  el0_svc+0x2c/0xc0
  el0t_64_sync_handler+0x1ac/0x1b0
  el0t_64_sync+0x19c/0x1a0
 ---[ end trace 0000000000000000 ]---

Fixes: 3fbf7f01

 ("coresight: sink: Add TRBE driver")
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Yang Shen <shenyang39@huawei.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20221122090355.23533-1-shenyang39@huawei.com