ACPI: Export interfaces for ioremapping/iounmapping ACPI registers

Export remapping and unmapping interfaces - acpi_os_map_generic_address()
and acpi_os_unmap_generic_address() - for ACPI generic registers that are
backed by memory mapped I/O (MMIO).

The acpi_os_map_generic_address() and acpi_os_unmap_generic_address()
declarations may more properly belong in include/acpi/acpiosxf.h next to
acpi_os_read_memory() but I believe that would require the ACPI CA making
them an official part of the ACPI CA - OS interface.

ACPI Generic Address Structure (GAS) reference (ACPI's fixed/generic
hardware registers use the GAS format):
  ACPI Specification, Revision 4.0, Section 5.2.3.1, "Generic Address
  Structure"

Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/include/linux/acpi_io.h b/include/linux/acpi_io.h
index 4afd7102..b0ffa21 100644
--- a/include/linux/acpi_io.h
+++ b/include/linux/acpi_io.h
@@ -12,4 +12,7 @@
 
 void __iomem *acpi_os_get_iomem(acpi_physical_address phys, unsigned int size);
 
+int acpi_os_map_generic_address(struct acpi_generic_address *addr);
+void acpi_os_unmap_generic_address(struct acpi_generic_address *addr);
+
 #endif