mm/alpha: unify mem_init() for both UMA and NUMA architectures

Now mem_init() for both Alpha UMA and Alpha NUMA are the same,
so unify it to reduce duplicated code.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: linux-alpha@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
mm/m68k: fix build warning of unused variable

Fix build warning of unused variable:
arch/m68k/mm/init.c: In function 'mem_init':
arch/m68k/mm/init.c:151:6: warning: unused variable 'i' [-Wunused-variable]

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@uclinux.org>
Cc: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Cc: linux-m68k@lists.linux-m68k.org
Cc: linux-kernel@vger.kernel.org