Add DDR3 support for AM335x-EVM (Version 1.5A)

Add DDR3 support for AM335x-EVM (Version 1.5A)

AM335x EVM 1.5A uses Micron MT41J512M8RH-125 SDRAM 4Gb (512Mx8) as the
DDR3 chip.

[Hebbar Gururaja <gururaja.hebbar@ti.com>]
	- Resolve merge conflict while rebasing. File structure is
	  changed in the mainline. So re-arrange the code accordingly.
	- Update commit message to reflect the DDR3 part number

Signed-off-by: Jeff Lance <j-lance1@ti.com>
Signed-off-by: Tom Rini <trini@ti.com>
Signed-off-by: Hebbar Gururaja <gururaja.hebbar@ti.com>