PCI/MSI: Consolidate error handling in msi_capability_init()

Three error exits doing exactly the same ask for a common error exit point.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210729222543.098828720@linutronix.de