drm/i915: extract intel_dp_mst.h from intel_drv.h

It used to be handy that we only had a couple of headers, but over time
intel_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/b2fd1b2b968aa0ce010d17e2811bc275cf9ca251.1556540890.git.jani.nikula@intel.com

drivers/gpu/drm/i915/Makefile.header-test

@@ -25,6 +25,7 @@ header_test := \
 	intel_dp.h \
 	intel_dp_aux_backlight.h \
 	intel_dp_link_training.h \
+	intel_dp_mst.h \
 	intel_dpll_mgr.h \
 	intel_drv.h \
 	intel_dsi.h \

drivers/gpu/drm/i915/intel_dp.c

@@ -48,6 +48,7 @@
 #include "intel_ddi.h"
 #include "intel_dp.h"
 #include "intel_dp_link_training.h"
+#include "intel_dp_mst.h"
 #include "intel_drv.h"
 #include "intel_fifo_underrun.h"
 #include "intel_hdcp.h"

drivers/gpu/drm/i915/intel_dp_mst.c

@@ -32,6 +32,7 @@
 #include "intel_connector.h"
 #include "intel_ddi.h"
 #include "intel_dp.h"
+#include "intel_dp_mst.h"
 #include "intel_drv.h"
 
 static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,

drivers/gpu/drm/i915/intel_dp_mst.h

+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#ifndef __INTEL_DP_MST_H__
+#define __INTEL_DP_MST_H__
+
+struct intel_digital_port;
+
+int intel_dp_mst_encoder_init(struct intel_digital_port *intel_dig_port, int conn_id);
+void intel_dp_mst_encoder_cleanup(struct intel_digital_port *intel_dig_port);
+
+#endif /* __INTEL_DP_MST_H__ */

drivers/gpu/drm/i915/intel_drv.h

@@ -1766,10 +1766,6 @@ unsigned int i9xx_plane_max_stride(struct intel_plane *plane,
 				   u32 pixel_format, u64 modifier,
 				   unsigned int rotation);
 
-/* intel_dp_mst.c */
-int intel_dp_mst_encoder_init(struct intel_digital_port *intel_dig_port, int conn_id);
-void intel_dp_mst_encoder_cleanup(struct intel_digital_port *intel_dig_port);
-
 /* intel_dsi_dcs_backlight.c */
 int intel_dsi_dcs_init_backlight_funcs(struct intel_connector *intel_connector);