OMAP3: 3430SDP: Fix defconfig

This patch makes the SDP boot again with the defconfig.

Changes done:

 - Removes other selected boards.
 - Sets the Low Level debug output for UART1.
 - Disables some paripherals from other boards.

Tested on a SDP3430-VE5.1.0 (OMAP3430 ES3.1)

Signed-off-by: Sergio Aguirre <saaguirre@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>