staging: fsl-mc: split mc-io definitions into a separate file

An mc-io is a software abstraction of a dpmcp object (an MC portal).
Routines to create/initialize/reset this portal abstraction were split
between the allocator and mc-sys.c (MC command interface).  Move
mc-io/portal related definitions into one source file.

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