ARM: OMAP5: Set fdt_high to enable booting with Device tree

While booting with dt blob, if fdt_high is not set to
0xffffffff, the dt blob gets relocated to a high ram address,
which the kernel is not able to use without HIGHMEM.

So set it to 0xffffffff to avoid the issue.

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