mm/kasan/init.c: remove unnecessary pointer variables

mm/kasan/init.c: remove unnecessary pointer variables

Simplify the code to enhance readability and maintain a consistent
coding style.

Link: https://lkml.kernel.org/r/20250811034257.154862-1-zhao.xichao@vivo.com
Signed-off-by: Xichao Zhao <zhao.xichao@vivo.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>