ARM: s3c44b0: remove remainders of dead board

Because commit 5dc5f36 removed B2 board support,
arch/arm/cpu/s3c44b0/* and arch/arm/include/asm/arch-s3c44b0/*
are not necessary anymore.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Andrea Scian <andrea.scian@dave-tech.it>