mtd: cfi_mtd: populate mtd->dev with flash_info->dev

Populate mtd->dev with flash_info->dev which allows to get
full mtd information using the "mtd list" command.
Before, "mtd list" command returns :

List of MTD devices:
* nor0
  - type: NOR flash
  - block size: 0x40000 bytes
  - min I/O: 0x1 bytes
  - 0x000000000000-0x000004000000 : "nor0"

After this patch we get for example:

List of MTD devices:
* nor0
  - device: flash@0
  - parent: spi@40430000
  - driver: cfi_flash
  - path: /soc/spi@40430000/flash@0
  - type: NOR flash
  - block size: 0x40000 bytes
  - min I/O: 0x1 bytes
  - 0x000000000000-0x000004000000 : "nor0"

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Stefan Roese <sr@denx.de>