Merge branches 'acpi-scan', 'acpi-bus', 'acpi-tables' and 'acpi-sysfs'

Merge ACPI changes related to device enumeration, device object
managenet, operation region handling, table parsing and sysfs
interface:

 - Use ZERO_PAGE(0) instead of empty_zero_page in the ACPI device
   enumeration code (Giulio Benetti).

 - Change the return type of the ACPI driver remove callback to void and
   update its users accordingly (Dawei Li).

 - Add general support for FFH address space type and implement the low-
   level part of it for ARM64 (Sudeep Holla).

 - Fix stale comments in the ACPI tables parsing code and make it print
   more messages related to MADT (Hanjun Guo, Huacai Chen).

 - Replace invocations of generic library functions with more kernel-
   specific counterparts in the ACPI sysfs interface (Christophe JAILLET,
   Xu Panda).

* acpi-scan:
  ACPI: scan: substitute empty_zero_page with helper ZERO_PAGE(0)

* acpi-bus:
  ACPI: FFH: Silence missing prototype warnings
  ACPI: make remove callback of ACPI driver void
  ACPI: bus: Fix the _OSC capability check for FFH OpRegion
  arm64: Add architecture specific ACPI FFH Opregion callbacks
  ACPI: Implement a generic FFH Opregion handler

* acpi-tables:
  ACPI: tables: Fix the stale comments for acpi_locate_initial_tables()
  ACPI: tables: Print CORE_PIC information when MADT is parsed

* acpi-sysfs:
  ACPI: sysfs: use sysfs_emit() to instead of scnprintf()
  ACPI: sysfs: Use kstrtobool() instead of strtobool()

drivers/platform/surface/surfacepro3_button.c

@@ -239,13 +239,12 @@ static int surface_button_add(struct acpi_device *device)
 	return error;
 }
 
-static int surface_button_remove(struct acpi_device *device)
+static void surface_button_remove(struct acpi_device *device)
 {
 	struct surface_button *button = acpi_driver_data(device);
 
 	input_unregister_device(button->input);
 	kfree(button);
-	return 0;
 }
 
 static SIMPLE_DEV_PM_OPS(surface_button_pm,