boards: microbit: Add flash partition definitions to dts
boards: microbit: Add flash partition definitions to dts

These are a direct copy from the nrf51_pca10028 board, since it's also
an nRF51 and has the same size flash.

Signed-off-by: Johan Hedberg <628991c7b0a19c384f9b99c21ec330ce952bb838@intel.com>

Vudentz/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,kraj/zephyr,mbolivar/zephyr,nashif/zephyr,zephyriot/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,mbolivar/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,mbolivar/zephyr,explora26/zephyr,zephyriot/zephyr,explora26/zephyr,finikorg/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,punitvara/zephyr,zephyriot/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,kraj/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,kraj/zephyr,Vudentz/zephyr,finikorg/zephyr,finikorg/zephyr,kraj/zephyr,nashif/zephyr,Vudentz/zephyr,zephyriot/zephyr,galak/zephyr,ldts/zephyr,explora26/zephyr,ldts/zephyr,punitvara/zephyr,explora26/zephyr,punitvara/zephyr,zephyriot/zephyr,punitvara/zephyr,ldts/zephyr,kraj/zephyr,explora26/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,mbolivar/zephyr