staging: fsl-mc: move couple of definitions to public header

Define dev_is_fsl_mc() and the bus type definition (fsl_mc_bus_type)
are used externally so move them to the public header.

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