Commit b5712bf8 ("irqchip/gic-v3-its: Provide MSI parent for
PCI/MSI[-X]") moves the functionality of irq-gic-v3-its-pci-msi.c into
irq-gic-v3-its-msi-parent.c, and drops the former file.

With that, the config option ARM_GIC_V3_ITS_PCI is obsolete, but the
definition of that config was not removed in the commit above.

Remove this obsolete config ARM_GIC_V3_ITS_PCI.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240926125502.363364-1-lukas.bulwahn@redhat.com