media: ddbridge: move MSI IRQ cleanup to a helper function

Introduce the ddb_msi_exit() helper to be used for cleaning up previously
allocated MSI IRQ vectors. Deduplicates code and makes things look
cleaner as for all cleanup work the CONFIG_PCI_MSI ifdeffery is only
needed in the helper now. Also, replace the call to the deprecated
pci_disable_msi() function with pci_free_irq_vectors().

Picked up from the upstream dddvb-0.9.33 release.

Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>