OMAP3: Add SPL_BOARD_INIT hook

Add an SPL_BOARD_INIT hook and for OMAP3 have it turn on i2c.  OMAP4
doesn't need i2c enabled in SPL.  Enable SPL_BOARD_INIT on devkit8000.

Cc: Frederik Kriewitz <frederik@kriewitz.eu>
Signed-off-by: Tom Rini <trini@ti.com>

arch/arm/include/asm/omap_common.h

@@ -94,6 +94,10 @@ void spl_nand_load_image(void);
 /* MMC SPL functions */
 void spl_mmc_load_image(void);
 
+#ifdef CONFIG_SPL_BOARD_INIT
+void spl_board_init(void);
+#endif
+
 /*
  * silicon revisions.
  * Moving this to common, so that most of code can be moved to common,