iommu/amd: Use `table' instead `irt' as variable name in amd_iommu_update_ga()

The variable of type struct irq_remap_table is always named `table'
except in amd_iommu_update_ga() where it is called `irt'. Make it
consistent and name it also `table'.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>