Revert "Fix the case BOARD_FLASH_BLOCK_SIZE smaller than BOARD_NAND_PAGE_SIZE, eg generic_x86"

# spare area for each page).

# $(1): the partition data size

define image-size-from-data-size

$(strip $(eval _isfds_value := $(shell echo $$(($(1) / $(BOARD_NAND_PAGE_SIZE) * \

  ($(BOARD_NAND_PAGE_SIZE)+$(BOARD_NAND_SPARE_SIZE))))))\

$(if $(filter 0, $(_isfds_value)),$(shell echo $$(($(BOARD_NAND_PAGE_SIZE)+$(BOARD_NAND_SPARE_SIZE)))),$(_isfds_value))\

$(eval _isfds_value :=))

$(shell echo $$(($(1) / $(BOARD_NAND_PAGE_SIZE) * \

  ($(BOARD_NAND_PAGE_SIZE)+$(BOARD_NAND_SPARE_SIZE)))))

endef

# $(1): The file(s) to check (often $@)