platform/x86: lenovo: wmi-gamezone: Drop gz_chain_head

The gz_chain_head variable has been unused since the driver's initial
addition to the tree. Its use was eliminated between v3 and v4 during
development but due to the reference of gz_chain_head's wait_list
member, the compiler could not warn that it was unused.

After a (tip) commit ("locking/rwsem: Remove the list_head from struct
rw_semaphore"), which removed a reference to the variable passed to
__RWSEM_INITIALIZER(), certain configurations show an unused variable
warning from the Lenovo wmi-gamezone driver:

  drivers/platform/x86/lenovo/wmi-gamezone.c:34:31: warning: 'gz_chain_head' defined but not used [-Wunused-variable]
     34 | static BLOCKING_NOTIFIER_HEAD(gz_chain_head);
        |                               ^~~~~~~~~~~~~
  include/linux/notifier.h:119:39: note: in definition of macro 'BLOCKING_NOTIFIER_HEAD'
    119 |         struct blocking_notifier_head name =                    \
        |                                       ^~~~

Remove the variable to prevent the warning from showing up.

Fixes: 22024ac ("platform/x86: Add Lenovo Gamezone WMI Driver")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Link: https://patch.msgid.link/20260313-lenovo-wmi-gamezone-remove-gz_chain_head-v1-1-ce5231f0c6fa@kernel.org
[ij: reorganized the changelog]
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: nathanchance

drivers/platform/x86/lenovo/wmi-gamezone.c

@@ -31,8 +31,6 @@
 #define LWMI_GZ_METHOD_ID_SMARTFAN_SET 44
 #define LWMI_GZ_METHOD_ID_SMARTFAN_GET 45
 
-static BLOCKING_NOTIFIER_HEAD(gz_chain_head);
-
 struct lwmi_gz_priv {
 	enum thermal_mode current_mode;
 	struct notifier_block event_nb;