drm/radeon/atombios_encoders: Move 'radeon_atom_get_tv_timings()'s prototype into shared location

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/radeon/radeon_atombios.c:1791:6: warning: no previous prototype for ‘radeon_atom_get_tv_timings’ [-Wmissing-prototypes]
 1791 | bool radeon_atom_get_tv_timings(struct radeon_device *rdev, int index,
 | ^~~~~~~~~~~~~~~~~~~~~~~~~~

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/atombios_encoders.c

@@ -33,6 +33,7 @@
 #include <drm/radeon_drm.h>
 
 #include "atom.h"
+#include "radeon_atombios.h"
 #include "radeon.h"
 #include "radeon_asic.h"
 #include "radeon_audio.h"
@@ -296,10 +297,6 @@ static void radeon_atom_backlight_exit(struct radeon_encoder *encoder)
 
 #endif
 
-/* evil but including atombios.h is much worse */
-bool radeon_atom_get_tv_timings(struct radeon_device *rdev, int index,
-				struct drm_display_mode *mode);
-
 static bool radeon_atom_mode_fixup(struct drm_encoder *encoder,
 				   const struct drm_display_mode *mode,
 				   struct drm_display_mode *adjusted_mode)

drivers/gpu/drm/radeon/radeon_atombios.c

@@ -34,6 +34,7 @@
 #include "atom.h"
 #include "atom-bits.h"
 #include "radeon_asic.h"
+#include "radeon_atombios.h"
 
 extern void
 radeon_add_atom_encoder(struct drm_device *dev, uint32_t encoder_enum,

drivers/gpu/drm/radeon/radeon_atombios.h

+/* radeon_atombios.h -- Private header for radeon driver -*- linux-c -*-
+ *
+ * Copyright 2007-8 Advanced Micro Devices, Inc.
+ * Copyright 2008 Red Hat Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: Dave Airlie
+ *          Alex Deucher
+ */
+
+#ifndef __RADEON_ATOMBIOS_H__
+#define __RADEON_ATOMBIOS_H__
+
+struct drm_display_mode;
+struct radeon_device;
+
+bool radeon_atom_get_tv_timings(struct radeon_device *rdev, int index,
+				struct drm_display_mode *mode);
+
+#endif                         /* __RADEON_ATOMBIOS_H__ */