ARM: OMAP2+: Drop legacy platform data for am3 emif

We can now probe devices with ti-sysc interconnect driver and dts
data. Let's drop the related platform data and custom ti,hwmods
dts property.

Cc: Dave Gerlach <d-gerlach@ti.com>
Cc: Suman Anna <s-anna@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>