staging: fsl-mc: Remove unnecessary dependency

The function that enables fsl-mc msi interrupts doesn't need
to be explicitly called from the fsl-mc bus driver initialization
routine.

Mark it to be independently called at system init; this is in line
with how things are handled by other GICv3 irqchip users.

Due to this change we now have an unused cleanup function, so
remove it.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Reviewed-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>