When enabling UBSAN_SANITIZE_ALL, the kernel image size gets increased
significantly (~3x).  So, it sounds better to have some note in Kconfig.

And, fixed a typo.
Signed-off-by: NYang Shi <yang.shi@linaro.org>
Acked-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>