subsys: storage: flash_map - Use correct macro
subsys: storage: flash_map - Use correct macro

Prior to this commit, the old `FLASH_DRIVER_NAME` macro was being used
in the definition of the flash drivers array.  This caused the array to
have a size of 0.

This commit changes the code to use the newer `FLASH_DEV_NAME` macro,
causing the configured flash device to be present in the table.

Signed-off-by: Christopher Collins <931fdb982a80bb744c6b95a3e1cdb3f421ab63fd@apache.org>

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