omap3_logic: Enable DM_SPI

With the introduction of ("Boards,Need,to,Switch,DM] spi: omap3_spi:
Full dm conversion"), Driver Model for McSPI is now available on the
omap3.  This enables the config by default on omap3_logic boards.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>