powerpc/T4240EMU: Add T4240EMU target

Add emulator support for T4240. Emulator has limited peripherals and
interfaces. Difference between emulator and T4240QDS includes:
	ECC for DDR is disabled due the procedure to load images
	No board FPGA (QIXIS)
	NOR flash has 32-bit port for higher loading speed
	IFC and I2C timing don't really matter, so set them fast
	No ethernet

Signed-off-by: York Sun <yorksun@freescale.com>