staging: fsl-mc: move bus private definitions into fsl-mc-bus.c

Move definitions that are private to fsl-mc-bus.c out of the
public mc-bus.h and mc.h headers.

Signed-off-by: Stuart Yoder <stuart.yoder@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>