selftests/ftrace: Add riscv support for kprobe arg tests

This is the riscv variant of commit 9855c462 ("selftests/ftrace:
Add ppc support for kprobe args tests").
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_char.tc

@@ -31,6 +31,9 @@ mips*)
 loongarch*)
   ARG1=%r4
 ;;
+riscv*)
+  ARG1=%a0
+;;
 *)
   echo "Please implement other architecture here"
   exit_untested

tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_string.tc

@@ -31,6 +31,9 @@ mips*)
 loongarch*)
   ARG1=%r4
 ;;
+riscv*)
+  ARG1=%a0
+;;
 *)
   echo "Please implement other architecture here"
   exit_untested

tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_syntax.tc

@@ -44,6 +44,10 @@ loongarch*)
   GOODREG=%r4
   BADREG=%r12
 ;;
+riscv*)
+  GOODREG=%a0
+  BADREG=%a8
+;;
 *)
   echo "Please implement other architecture here"
   exit_untested