arch-riscv: Add an implementation of set_tid_address syscall in RISCV

Change-Id: Ida29ea6f6a9c3efe00aaebbfcb6b537fc62f6d06
Reviewed-on: https://gem5-review.googlesource.com/6901
Reviewed-by: Alec Roelke <ar4jc@virginia.edu>
Maintainer: Alec Roelke <ar4jc@virginia.edu>

src/arch/riscv/linux/process.cc

@@ -165,7 +165,7 @@ std::map<int, SyscallDesc> RiscvLinuxProcess::syscallDescs = {
     {93,   SyscallDesc("exit", exitFunc)},
     {94,   SyscallDesc("exit_group", exitGroupFunc)},
     {95,   SyscallDesc("waitid")},
-    {96,   SyscallDesc("set_tid_address")},
+    {96,   SyscallDesc("set_tid_address", setTidAddressFunc)},
     {97,   SyscallDesc("unshare")},
     {98,   SyscallDesc("futex", futexFunc<RiscvLinux>)},
     {99,   SyscallDesc("set_robust_list")},