ACPI: Pre-map 'system event' related register blocks
During ACPI initialization, pre-map fixed hardware registers that are
accessed during ACPI's 'system event' related IRQ handing.
ACPI's 'system event' handing accesses specific fixed hardware
registers; namely PM1a event, PM1b event, GPE0, and GPE1 register
blocks which are declared within the FADT. If these registers are
backed by MMIO, as opposed to I/O port space, accessing them within
interrupt context will cause a panic as acpi_os_read_memory()
depends on ioremap() in such cases - BZ 18012.
By utilizing the functionality provided in the previous two patches -
ACPI: Maintain a list of ACPI memory mapped I/O remappings, and, ACPI:
Add interfaces for ioremapping/iounmapping ACPI registers - accesses
to ACPI MMIO areas will now be safe from within interrupt contexts (IRQ
and/or NMI) provided the area was pre-mapped. This solves BZ 18012.