unwind: repair register restoration for OR1K

Currently, OR1K architecture put the program counter at offset 0x128 of
the current `or1k_thread_state_t`. However, the PC is restored after
updating the thread pointer in `r3`, which causes the PC to be fetched
incorrectly.

This patch swaps the order of restoration of `r9` and `r3`, such that
the PC is restored to `r9` using the current thread state.

Patch by Oi Chee Cheung!

Reviewed By: whitequark, compnerd

Differential Revision: https://reviews.llvm.org/D107042