drm/radeon: move com/atombios scratch reg functions to radeon_mode.h

fixes warnings with -Wmissing-prototypes

Based on initial patches from Rashika Kheria.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Rashika Kheria <rashika.kheria@gmail.com>

drivers/gpu/drm/radeon/radeon_connectors.c

@@ -33,15 +33,6 @@
 
 #include <linux/pm_runtime.h>
 
-extern void
-radeon_combios_connected_scratch_regs(struct drm_connector *connector,
-				      struct drm_encoder *encoder,
-				      bool connected);
-extern void
-radeon_atombios_connected_scratch_regs(struct drm_connector *connector,
-				       struct drm_encoder *encoder,
-				       bool connected);
-
 void radeon_connector_hotplug(struct drm_connector *connector)
 {
 	struct drm_device *dev = connector->dev;

drivers/gpu/drm/radeon/radeon_mode.h

@@ -631,6 +631,15 @@ radeon_atombios_get_tv_info(struct radeon_device *rdev);
 extern void radeon_atombios_get_default_voltages(struct radeon_device *rdev,
 						 u16 *vddc, u16 *vddci, u16 *mvdd);
 
+extern void
+radeon_combios_connected_scratch_regs(struct drm_connector *connector,
+				      struct drm_encoder *encoder,
+				      bool connected);
+extern void
+radeon_atombios_connected_scratch_regs(struct drm_connector *connector,
+				       struct drm_encoder *encoder,
+				       bool connected);
+
 extern struct drm_connector *
 radeon_get_connector_for_encoder(struct drm_encoder *encoder);
 extern struct drm_connector *