staging: fsl-mc: set MSI domain for DPRC objects

THE MSI domain associated with a root DPRC object is
obtained form the device tree. Child DPRCs inherit
the parent DPRC MSI domain.

Signed-off-by: J. German Rivera <German.Rivera@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>