staging: fsl-mc: Cleanup dprc and dpmcp header files

A lot of API and associated structures are not used by current code, so
remove them.

Signed-off-by: Bogdan Purcareata <bogdan.purcareata@nxp.com>
Reviewed-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>