iwlwifi: mvm: Fix thermal zone registration

Use a unique name when registering a thermal zone. Otherwise, with
multiple NICS, we hit the following warning during the unregistration.

WARNING: CPU: 2 PID: 3525 at fs/sysfs/group.c:255
 RIP: 0010:sysfs_remove_group+0x80/0x90
 Call Trace:
  dpm_sysfs_remove+0x57/0x60
  device_del+0x5a/0x350
  ? sscanf+0x4e/0x70
  device_unregister+0x1a/0x60
  hwmon_device_unregister+0x4a/0xa0
  thermal_remove_hwmon_sysfs+0x175/0x1d0
  thermal_zone_device_unregister+0x188/0x1e0
  iwl_mvm_thermal_exit+0xe7/0x100 [iwlmvm]
  iwl_op_mode_mvm_stop+0x27/0x180 [iwlmvm]
  _iwl_op_mode_stop.isra.3+0x2b/0x50 [iwlwifi]
  iwl_opmode_deregister+0x90/0xa0 [iwlwifi]
  __exit_compat+0x10/0x2c7 [iwlmvm]
  __x64_sys_delete_module+0x13f/0x270
  do_syscall_64+0x5a/0x110
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>