drm/msm: Restore second parameter name in purge() and evict()

[ Upstream commit 53676e4d44d6b38c8a0d9bff331f170ae2e41bbe ]

After commit 3392291fc509 ("drm/msm: Fix shrinker deadlock"), all
supported versions of clang warn (or error with CONFIG_WERROR=y):

  drivers/gpu/drm/msm/msm_gem_shrinker.c:105:58: error: omitting the parameter name in a function definition is a C23 extension [-Werror,-Wc23-extensions]
    105 | purge(struct drm_gem_object *obj, struct ww_acquire_ctx *)
        |                                                          ^
  drivers/gpu/drm/msm/msm_gem_shrinker.c:117:58: error: omitting the parameter name in a function definition is a C23 extension [-Werror,-Wc23-extensions]
    117 | evict(struct drm_gem_object *obj, struct ww_acquire_ctx *)
        |                                                          ^
  2 errors generated.

With older but supported versions of GCC, this is an unconditional hard error:

  drivers/gpu/drm/msm/msm_gem_shrinker.c: In function 'purge':
  drivers/gpu/drm/msm/msm_gem_shrinker.c:105:35: error: parameter name omitted
   purge(struct drm_gem_object *obj, struct ww_acquire_ctx *)
                                     ^~~~~~~~~~~~~~~~~~~~~~~
  drivers/gpu/drm/msm/msm_gem_shrinker.c: In function 'evict':
  drivers/gpu/drm/msm/msm_gem_shrinker.c:117:35: error: parameter name omitted
   evict(struct drm_gem_object *obj, struct ww_acquire_ctx *)
                                     ^~~~~~~~~~~~~~~~~~~~~~~

Restore the parameter name to clear up the warnings, renaming it
"unused" to make it clear it is only needed to satisfy the prototype of
drm_gem_lru_scan().

Cc: stable@vger.kernel.org
Fixes: 3392291fc509 ("drm/msm: Fix shrinker deadlock")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 239172639075ef745ca233386086ba4b2b5077f8)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>

Author: nathanchance

drivers/gpu/drm/msm/msm_gem_shrinker.c

@@ -102,7 +102,7 @@ with_vm_locks(void (*fn)(struct drm_gem_object *obj),
 }
 
 static bool
-purge(struct drm_gem_object *obj, struct ww_acquire_ctx *)
+purge(struct drm_gem_object *obj, struct ww_acquire_ctx *unused)
 {
 	if (!is_purgeable(to_msm_bo(obj)))
 		return false;
@@ -114,7 +114,7 @@ purge(struct drm_gem_object *obj, struct ww_acquire_ctx *)
 }
 
 static bool
-evict(struct drm_gem_object *obj, struct ww_acquire_ctx *)
+evict(struct drm_gem_object *obj, struct ww_acquire_ctx *unused)
 {
 	if (is_unevictable(to_msm_bo(obj)))
 		return false;