board: omapl138_lcdk: add the mmc device to SPL

We don't have full device-tree support in SPL yet - add an appropriate
U_BOOT_DEVICE() to the board file.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
diff --git a/arch/arm/mach-davinci/Kconfig b/arch/arm/mach-davinci/Kconfig
index adc5092..8a81c07 100644
--- a/arch/arm/mach-davinci/Kconfig
+++ b/arch/arm/mach-davinci/Kconfig
@@ -14,6 +14,7 @@
 	bool "OMAPL138 LCDK"
 	select SOC_DA8XX
 	select SUPPORT_SPL
+	select SPL_BOARD_INIT
 
 config TARGET_LEGOEV3
 	bool "LEGO MINDSTORMS EV3"