U-Boot/SPL: omap4: Make ddr pre-calculated timings as default.

All ddr configurations(geometry/timings) are done automatically
by detecting the device connected at run time. Though this
is a useful feature, making this as a default setting increases
the code size by about 2K bytes. This is quite big, especially
in the case of SPL which runs from a smaller SRAM. So do not
use this feature as the default setting, instead use the
precalculated tables.

Signed-off-by: sricharan <r.sricharan@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>