[llvm] [RISC-V] Adjust trampoline code for branch control flow protection (PR #141949)

[Jesse Huang via llvm-commits]

jaidTw wrote:

There is a chang to use software-guarded jump (t2) in the trampoline code, the new stack of the test is now
```
   56 $ra
   44 $a0      f
   36 $a1      p
   32 00038067 jalr  t2
   28 010e3e03 ld    t3, 16(t3)
   24 018e3383 ld    t2, 24(t3)
   20 00000e17 auipc t3, 0
sp+16 00000023 lpad  0
```

https://github.com/llvm/llvm-project/pull/141949