ARM: OMAP2+: Remove unused ti81xx platform init code

The support for 81xx was never working in mainline, and the broken
legacy booting support has been removed. There are patches coming
to make 81xx boot with device tree, and for that we won't need any
of this legacy platform code, so let's just remove it.

Cc: Brian Hutchinson <b.hutchman@gmail.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>