So with OMAP added to multi platform kernel,
the uImage no more contains a valid load address.
With the uboot already supporting zImage,
change the default boot command to bootz
instead.

Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Sricharan R <r.sricharan@ti.com>
Tested-by: Nishanth Menon <nm@ti.com>