soc: telink: tlsr951x: use RISC-V custom CSR common code

TLSR951x also supports Andes extended CSR. Reworks the following CSR
handling to use the RISC-V custom CSR common code:

1. Use common macros for HWDSP CSR context save/restore.
2. Use common macros for PFT CSR context save/restore.
3. Use common low-level CSR initialization via __reset hook.

Signed-off-by: Jimmy Zheng <jimmyzhe@andestech.com>
9 files changed