ACPI: Replace irqdomain.h include with struct declarations

linux/acpi.h includes irqdomain.h which includes of.h. Break the include
chain by replacing the irqdomain include with forward declarations for
struct irq_domain and irq_domain_ops which is sufficient for acpi.h.

of.h also includes mod_devicetable.h which many drivers implicitly
depend on. As acpi.h already includes it, just move it out of the
'#ifdef CONFIG_ACPI'.
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/acpi.h

@@ -10,12 +10,15 @@
 
 #include <linux/errno.h>
 #include <linux/ioport.h>	/* for struct resource */
-#include <linux/irqdomain.h>
 #include <linux/resource_ext.h>
 #include <linux/device.h>
+#include <linux/mod_devicetable.h>
 #include <linux/property.h>
 #include <linux/uuid.h>
 
+struct irq_domain;
+struct irq_domain_ops;
+
 #ifndef _LINUX
 #define _LINUX
 #endif
@@ -24,7 +27,6 @@
 #ifdef	CONFIG_ACPI
 
 #include <linux/list.h>
-#include <linux/mod_devicetable.h>
 #include <linux/dynamic_debug.h>
 #include <linux/module.h>
 #include <linux/mutex.h>