[PATCH v2] drm/i915: Disable -Wuninitialized

[Nathan Chancellor <natechancellor@gmail.com>]

This warning is disabled by default in scripts/Makefile.extrawarn when
W= is not provided but this Makefile adds -Wall after this warning is
disabled so it shows up in the build when it shouldn't:

In file included from drivers/gpu/drm/i915/intel_breadcrumbs.c:895:
drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c:350:34: error:
variable 'wq' is uninitialized when used within its own initialization
[-Werror,-Wuninitialized]
        DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
                                        ^~
./include/linux/wait.h:74:63: note: expanded from macro
'DECLARE_WAIT_QUEUE_HEAD_ONSTACK'
        struct wait_queue_head name = __WAIT_QUEUE_HEAD_INIT_ONSTACK(name)
                               ~~~~                                  ^~~~
./include/linux/wait.h:72:33: note: expanded from macro
'__WAIT_QUEUE_HEAD_INIT_ONSTACK'
        ({ init_waitqueue_head(&name); name; })
                                       ^~~~
1 error generated.

Explicitly disable the warning like commit 46e2068081e9 ("drm/i915:
Disable some extra clang warnings").

Link: https://github.com/ClangBuiltLinux/linux/issues/220
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---

v1 -> v2:

* Rather than disable the warning for the problematic folder, disable it
  for the entire folder like Matthias's commit.

 drivers/gpu/drm/i915/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 8300efe60fe1..210d0e8777b6 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -22,6 +22,7 @@ subdir-ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
 subdir-ccflags-y += $(call cc-disable-warning, sign-compare)
 subdir-ccflags-y += $(call cc-disable-warning, sometimes-uninitialized)
 subdir-ccflags-y += $(call cc-disable-warning, initializer-overrides)
+subdir-ccflags-y += $(call cc-disable-warning, uninitialized)
 subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
 
 # Fine grained warnings disable
-- 
2.20.1