lib/Kconfig.debug: disable -Wframe-larger-than warnings with KASAN=y

lib/Kconfig.debug: disable -Wframe-larger-than warnings with KASAN=y

When the kernel compiled with KASAN=y, GCC adds redzones for each
variable on stack.  This enlarges function's stack frame and causes:

	'warning: the frame size of X bytes is larger than Y bytes'

The worst case I've seen for now is following:

   ../net/wireless/nl80211.c: In function `nl80211_send_wiphy':
   ../net/wireless/nl80211.c:1731:1: warning: the frame size of 5448 bytes is larger than 2048 bytes [-Wframe-larger-than=]

That kind of warning becomes useless with KASAN=y.  It doesn't
necessarily indicate that there is some problem in the code, thus we
should turn it off.

(The KASAN=y stack size in increased from 16k to 32k for this reason)

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: Abylay Ospan <aospan@netup.ru>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
Cc: Kozlov Sergey <serjk@netup.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[Backport from mainline to remove build warning from KASAN option with GCC 6]
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Change-Id: I765080564f7b312fd48988b2f70aaa6f9b2eb71c