ACPI: fix section mis-match build warning

Dunno why this pops out in only in the allmodconfig build.
Though the warning is accurate, all the callers of the flagged
non __init function are __init, this is not a functional change.

WARNING: vmlinux - Section mismatch: reference to .init.data:acpi_sci_flags from .text between 'acpi_sci_ioapic_setup' (at offset 0xc010f0a
6) and 'acpi_gsi_to_irq'                                                                                                                   WARNING: vmlinux - Section mismatch: reference to .init.text:mp_override_legacy_irq from .text between 'acpi_sci_ioapic_setup' (at offset 0
xc010f0de) and 'acpi_gsi_to_irq'                                                                                                           WARNING: vmlinux - Section mismatch: reference to .init.data:acpi_sci_override_gsi from .text between 'acpi_sci_ioapic_setup' (at offset 0x
c010f0e4) and 'acpi_gsi_to_irq'

Signed-off-by: Len Brown <len.brown@intel.com>