boards: st: stm32h7RS target boards has pyocd runner

Add the pyocd as runner for the stm32h7s3l8 nucleo or stm32h7s78 dk
so that debugging becomes possible if openocd is not available.
Check with 'pyocd list --target'

Signed-off-by: Francois Ramu <francois.ramu@st.com>