drm/radeon/dpm: fix compilation with certain versions of gcc

Add #include <linux/seq_file.h> to *_dpm.c files
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/ni_dpm.c

@@ -28,6 +28,7 @@
 #include "ni_dpm.h"
 #include "atom.h"
 #include <linux/math64.h>
+#include <linux/seq_file.h>
 
 #define MC_CG_ARB_FREQ_F0           0x0a
 #define MC_CG_ARB_FREQ_F1           0x0b

drivers/gpu/drm/radeon/rv6xx_dpm.c

@@ -28,6 +28,7 @@
 #include "r600_dpm.h"
 #include "rv6xx_dpm.h"
 #include "atom.h"
+#include <linux/seq_file.h>
 
 static u32 rv6xx_scale_count_given_unit(struct radeon_device *rdev,
 					u32 unscaled_count, u32 unit);

drivers/gpu/drm/radeon/rv770_dpm.c

@@ -29,6 +29,7 @@
 #include "rv770_dpm.h"
 #include "cypress_dpm.h"
 #include "atom.h"
+#include <linux/seq_file.h>
 
 #define MC_CG_ARB_FREQ_F0           0x0a
 #define MC_CG_ARB_FREQ_F1           0x0b

drivers/gpu/drm/radeon/si_dpm.c

@@ -28,6 +28,7 @@
 #include "si_dpm.h"
 #include "atom.h"
 #include <linux/math64.h>
+#include <linux/seq_file.h>
 
 #define MC_CG_ARB_FREQ_F0           0x0a
 #define MC_CG_ARB_FREQ_F1           0x0b

drivers/gpu/drm/radeon/sumo_dpm.c

@@ -27,6 +27,7 @@
 #include "r600_dpm.h"
 #include "cypress_dpm.h"
 #include "sumo_dpm.h"
+#include <linux/seq_file.h>
 
 #define SUMO_MAX_DEEPSLEEP_DIVIDER_ID 5
 #define SUMO_MINIMUM_ENGINE_CLOCK 800

drivers/gpu/drm/radeon/trinity_dpm.c

@@ -26,6 +26,7 @@
 #include "trinityd.h"
 #include "r600_dpm.h"
 #include "trinity_dpm.h"
+#include <linux/seq_file.h>
 
 #define TRINITY_MAX_DEEPSLEEP_DIVIDER_ID 5
 #define TRINITY_MINIMUM_ENGINE_CLOCK 800