remoteproc/omap: Remove the platform_data header

The platform data header for OMAP remoteproc is no longer used for
anything post ti-sysc and DT conversion, so just remove it completely.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Suman Anna <s-anna@ti.com>
Reviewed-by: Andrew F. Davis <afd@ti.com>
Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200324110035.29907-9-t-kristo@ti.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>