mtd: spi: Kconfig: Imply SPI_FLASH if DM_SPI_FLASH

DM_SPI_FLASH should require spi flash interface code for dm
version, so imply SPI_FLASH core by default if any board
enabled DM_SPI_FLASH.

This overcome the explicit enablement of CONFIG_SPI_FLASH on
respective boards when DM_SPI_FLASH being used.

Acked-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/drivers/mtd/spi/Kconfig b/drivers/mtd/spi/Kconfig
index a0cfc62..681dc9c 100644
--- a/drivers/mtd/spi/Kconfig
+++ b/drivers/mtd/spi/Kconfig
@@ -3,6 +3,7 @@
 config DM_SPI_FLASH
 	bool "Enable Driver Model for SPI flash"
 	depends on DM && DM_SPI
+	imply SPI_FLASH
 	help
 	  Enable driver model for SPI flash. This SPI flash interface
 	  (spi_flash_probe(), spi_flash_write(), etc.) is then