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: NTom Rini <trini@ti.com>