devkit8000: protect board_mmc_init

This function is also defined in omap-common/spl_mmc.de so the implementation
in devkit8000.c was protected by a ifdef.

Signed-off-by: Simon Schwarz <simonschwarzcor@gmail.com>

board/timll/devkit8000/devkit8000.c

@@ -120,7 +120,7 @@ void set_muxconf_regs(void)
 	MUX_DEVKIT8000();
 }
 
-#ifdef CONFIG_GENERIC_MMC
+#if defined(CONFIG_GENERIC_MMC) && !defined(CONFIG_SPL_BUILD)
 int board_mmc_init(bd_t *bis)
 {
 	omap_mmc_init(0);