Kbuild: enable -Wmaybe-uninitialized warnings by default

Previously the warnings were added back at the W=1 level and above, this
now turns them on again by default, assuming that we have addressed all
warnings and again have a clean build for v4.10.

I found a number of new warnings in linux-next already and submitted
bugfixes for those.  Hopefully they are caught by the 0day builder in
the future as soon as this patch is merged.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/Makefile.extrawarn

@@ -60,8 +60,6 @@ endif
 KBUILD_CFLAGS += $(warning)
 else
 
-KBUILD_CFLAGS += $(call cc-disable-warning, maybe-uninitialized)
-
 ifeq ($(cc-name),clang)
 KBUILD_CFLAGS += $(call cc-disable-warning, initializer-overrides)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-value)