doc: fix riscv commands

doc: fix riscv commands

- Fix the declaration of riscv command 'set_mem_access'.
- Remove non existing riscv command 'set_scratch_ram'.
- Add riscv commands 'info', 'reset_delays'; copy the description
  from the 'help' text.
- Don't add riscv commands 'set_prefer_sba' and 'test_sba_config_reg'
  as they are marked as deprecated.
- Ensure that 'test_sba_config_reg' prints a deprecation warning
  when used.

Change-Id: I39dc3aec4e7f13b69ac19685f1b593790acdde83
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Signed-off-by: Jan Matyas <matyas@codasip.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7268
Reviewed-by: Tim Newsome <tim@sifive.com>
Tested-by: jenkins