unicore32-oldabi: add oldabi syscall interface

v2: Change current_thread_info()->restart_block to current->restart_block in signal.c
According to commit f56141e3


	all arches, signal: move restart_block to struct task_struct

Signed-off-by: Guenter Roeck <linux@roeck-us.net>

v1: Define unicore32 oldabi syscall in
	arch/unicore32/include/uapi/asm/unistd-oldabi.h.
And implement some architecture related syscalls.

Signed-off-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: Qin Rui <qinrui@pku.edu.cn>
Tested-by: Guenter Roeck <linux@roeck-us.net>