Removing dead OMAP_DSP

OMAP_DSP doesn't exist in Kconfig, therefore removing all
references for it from the source code.

Signed-off-by: Christoph Egger <siccegge@cs.fau.de>
[tony@atomide.com: updated to apply on top of already queued patches]
Signed-off-by: Tony Lindgren <tony@atomide.com>