Add note to SPI example.
Add note to SPI example.

iabdalkader/openmv,openmv/openmv,openmv/openmv,iabdalkader/openmv,openmv/openmv,kwagyeman/openmv,iabdalkader/openmv,openmv/openmv,iabdalkader/openmv,kwagyeman/openmv,kwagyeman/openmv,kwagyeman/openmv