mvebu: consolidate SPL boot device config symbols

Use MVEBU_SPL_BOOT_DEVICE_* to select between SPI and MMC, instead of
board specific symbols. This commit enables the boot device selection
menu to all mvebu platforms, but it is only effective on Turris Omnia
and gdsys Controlcenter DC platforms. A following commit will enable
boot selection for other platforms.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/arch/arm/mach-mvebu/Kconfig b/arch/arm/mach-mvebu/Kconfig
index e340a9b..e1b70c5 100644
--- a/arch/arm/mach-mvebu/Kconfig
+++ b/arch/arm/mach-mvebu/Kconfig
@@ -183,21 +183,18 @@
 config SYS_SOC
 	default "mvebu"
 
-if TARGET_TURRIS_OMNIA
-
 choice
-	prompt "Turris Omnia boot method"
+	prompt "Boot method"
 
-config TURRIS_OMNIA_SPL_BOOT_DEVICE_SPI
+config MVEBU_SPL_BOOT_DEVICE_SPI
 	bool "SPI NOR flash"
 
-config TURRIS_OMNIA_SPL_BOOT_DEVICE_MMC
+config MVEBU_SPL_BOOT_DEVICE_MMC
 	bool "SDIO/MMC card"
+	select SPL_LIBDISK_SUPPORT
 
 endchoice
 
-endif
-
 config MVEBU_EFUSE
 	bool "Enable eFuse support"
 	default n