riscv: Fix ftrace syscall handling which are now prefixed with __riscv_

riscv: Fix ftrace syscall handling which are now prefixed with __riscv_

ftrace creates entries for each syscall in the tracefs but has failed
since commit 08d0ce30e0e4 ("riscv: Implement syscall wrappers") which
prefixes all riscv syscalls with __riscv_.

So fix this by implementing arch_syscall_match_sym_name() which allows us
to ignore this prefix.

And also ignore compat syscalls like x86/arm64 by implementing
arch_trace_is_compat_syscall().

Fixes: 08d0ce30e0e4 ("riscv: Implement syscall wrappers")
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20231003182407.32198-1-alexghiti@rivosinc.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>