iommu/vt-d: Propagate error-value from ir_parse_ioapic_hpet_scope()

Propagate the error-value from the function ir_parse_ioapic_hpet_scope()
in parse_ioapics_under_ir() and cleanup its calling loop.

Signed-off-by: Joerg Roedel <jroedel@suse.de>