fs: littlefs: force alignment for buffers
fs: littlefs: force alignment for buffers

At least one flash driver requires that the source and destination
buffers be word-aligned.  Annotate the synthesized definitions to make
sure this happens.

Signed-off-by: Peter Bigot <a4112a160b558d5427af084318038e19a95979ee@nordicsemi.no>

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