samples: drivers: spi_flash rename definitions
samples: drivers: spi_flash rename definitions

This commits prefixes all the definitions
with 'SPI_' to be used by the sample application.
This will avoid compilation conflict especially
on FLASH_SECTOR_SIZE.

Signed-off-by: Francois Ramu <b83adc7f8a23ee911a37fcb61c4033581aae0b7a@st.com>

zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr