MAINTAINERS: update KASAN file list

Account for the following files:

 - lib/Kconfig.kasan

 - lib/test_kasan_module.c

 - arch/arm64/include/asm/mte-kasan.h

Link: https://lkml.kernel.org/r/7f9771d97b34d396bfdc4e288ad93486bb865a06.1613150186.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>