drm/amd/display: Remove useless defines

Remove __cplusplus defines added by accident.
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/spl/dc_spl.h

@@ -9,16 +9,8 @@
 #define BLACK_OFFSET_RGB_Y 0x0
 #define BLACK_OFFSET_CBCR  0x8000
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* SPL interfaces */
 
 bool spl_calculate_scaler_params(struct spl_in *spl_in, struct spl_out *spl_out);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* __DC_SPL_H__ */