PCI: MSI: Fix Kconfig dependencies for PCI_MSI_ARCH_FALLBACKS

The unconditional selection of PCI_MSI_ARCH_FALLBACKS has an unmet
dependency because PCI_MSI_ARCH_FALLBACKS is defined in a 'if PCI' clause.

As it is only relevant when PCI_MSI is enabled, update the affected
architecture Kconfigs to make the selection of PCI_MSI_ARCH_FALLBACKS
depend on 'if PCI_MSI'.

Fixes: 077ee78e ("PCI/MSI: Make arch_.*_msi_irq[s] fallbacks selectable")
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Links: https://lore.kernel.org/r/cdfd63305caa57785b0925dd24c0711ea02c8527.camel@redhat.com