MIPS: Use arch specific syscall name match function

On MIPS system, most of the syscall function name begin with prefix
sys_. Some syscalls are special such as clone/fork, function name of
these begin with __sys_. Since scratch registers need be saved in
stack when these system calls happens.

With ftrace system call method, system call functions are declared with
SYSCALL_DEFINEx, metadata of the system call symbol name begins with
sys_. Here mips specific function arch_syscall_match_sym_name is used to
compare function name between sys_call_table[] and metadata of syscall
symbol.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>