staging: tidspbridge: remove unnecessary include of <plat/clock.h>

The DSPBridge driver includes arch/arm/plat-omap/include/plat/clock.h.
All of the <plat/ ...> includes are causing problems with the ARM
single image kernel effort.  Remove this one.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>