ARM: OMAP: TI814X: Create board support and enable build for TI8148 EVM

This patch adds minimal support and build configuration for TI8148 EVM. Also
adds support for low level debugging on UART1 console on the EVM.

Note that existing TI8168 EVM file (board-ti8168evm.c) is updated with machine
info for TI8148 EVM.

Signed-off-by: Hemant Pedanekar <hemantp@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>