staging: fsl-mc: properly set hwirq in msi set_desc

For an MSI domain the hwirq is an arbitrary but unique
id to identify an interrupt.  Previously the hwirq was set to
the MSI index of the interrupt, but that only works if there is
one DPRC.  Additional DPRCs require an expanded namespace.  Use
both the ICID (which is unique per DPRC) and the MSI index to
compose a hwirq value.

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