hal_flash is unused, remove the import.
hal_flash is unused, remove the import.

All code referencing hal_flash functions was previously removed.

Signed-off-by: Blaž Hrastnik <184911b3f7af7b8aac99583da7ddfd77cc80c16c@mxxn.io>

runtimeco/mcuboot,tamban01/mcuboot,runtimeco/mcuboot,utzig/mcuboot,ATmobica/mcuboot,ATmobica/mcuboot,utzig/mcuboot,utzig/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot,runtimeco/mcuboot,tamban01/mcuboot,ATmobica/mcuboot,utzig/mcuboot,tamban01/mcuboot,tamban01/mcuboot,runtimeco/mcuboot,tamban01/mcuboot,ATmobica/mcuboot,utzig/mcuboot