riscv: entry: Add noinstr to prevent instrumentation inserted

riscv: entry: Add noinstr to prevent instrumentation inserted

Without noinstr the compiler is free to insert instrumentation (think
all the k*SAN, KCov, GCov, ftrace etc..) which can call code we're not
yet ready to run this early in the entry path, for instance it could
rely on RCU which isn't on yet, or expect lockdep state. (by peterz)

Link: https://lore.kernel.org/linux-riscv/YxcQ6NoPf3AH0EXe@hirez.programming.kicks-ass.net/
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20230222033021.983168-4-guoren@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>