dts/arm/st: stm32f3: Provide erase and write block size
dts/arm/st: stm32f3: Provide erase and write block size

On currently supported stm32f3 chips,
erase-block-size = 2048
write-block-size = 2
Set these property in stm32f3 series root dtsi file.

Fixes #9686

Signed-off-by: Erwan Gouriou <de4d967452b83bb0e37525652734e7d9163b6a4c@linaro.org>

galak/zephyr,nashif/zephyr,ldts/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,ldts/zephyr,ldts/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,ldts/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr