staging: fsl-mc: fix compilation with non-generic msi domain ops

The bus driver relies on generic msi domain ops.
Fix compilation for architectures that don't provide it (e.g. x86_64).

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>