genirq/msi, platform-msi: Ensure that MSI descriptors are unreferenced

Miquel reported a warning in the MSI core which is triggered when
interrupts are freed via platform_msi_device_domain_free().

This code got reworked to use core functions for freeing the MSI
descriptors, but nothing took care to clear the msi_desc->irq entry, which
then triggers the warning in msi_free_msi_desc() which uses desc->irq to
validate that the descriptor has been torn down. The same issue exists in
msi_domain_populate_irqs().

Up to the point that msi_free_msi_descs() grew a warning for this case,
this went un-noticed.

Provide the counterpart of msi_domain_populate_irqs() and invoke it in
platform_msi_device_domain_free() before freeing the interrupts and MSI
descriptors and also in the error path of msi_domain_populate_irqs().

Fixes: 2f2940d1

 ("genirq/msi: Remove filter from msi_free_descs_free_range()")
Reported-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/87mt4wkwnv.ffs@tglx