drm/i915: extract i915_suspend.h from i915_drv.h

It used to be handy that we only had a couple of headers, but over time
i915_drv.h has become unwieldy. Extract declarations to a separate
header file corresponding to the implementation module, clarifying the
modularity of the driver.

Ensure the new header is self-contained, and do so with minimal further
includes, using forward declarations as needed. Include the new header
only where needed, and sort the modified include directives while at it
and as needed.

No functional changes.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/94f2884a3e5611c3e1f015104afb965e47bd8992.1565271681.git.jani.nikula@intel.com

drivers/gpu/drm/i915/i915_drv.c

@@ -70,6 +70,7 @@
 #include "i915_irq.h"
 #include "i915_perf.h"
 #include "i915_query.h"
+#include "i915_suspend.h"
 #include "i915_sysfs.h"
 #include "i915_trace.h"
 #include "i915_vgpu.h"

drivers/gpu/drm/i915/i915_drv.h

@@ -2499,10 +2499,6 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 			    u32 batch_len,
 			    bool is_master);
 
-/* i915_suspend.c */
-int i915_save_state(struct drm_i915_private *dev_priv);
-int i915_restore_state(struct drm_i915_private *dev_priv);
-
 /* intel_device_info.c */
 static inline struct intel_device_info *
 mkwrite_device_info(struct drm_i915_private *dev_priv)

drivers/gpu/drm/i915/i915_suspend.c

@@ -31,6 +31,7 @@
 
 #include "i915_drv.h"
 #include "i915_reg.h"
+#include "i915_suspend.h"
 
 static void i915_save_display(struct drm_i915_private *dev_priv)
 {

drivers/gpu/drm/i915/i915_suspend.h

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#ifndef __I915_SUSPEND_H__
+#define __I915_SUSPEND_H__
+
+struct drm_i915_private;
+
+int i915_save_state(struct drm_i915_private *i915);
+int i915_restore_state(struct drm_i915_private *i915);
+
+#endif /* __I915_SUSPEND_H__ */