drm/amd/display: Remove incorrect macro guard

This macro guard "__cplusplus" is unnecessary and should not be there.

Signed-off-by: Alex Hung <alex.hung@amd.com>
Reviewed-by: Rodrigo Siqueira <siqueira@igalia.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Alex Hung

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

@@ -17,9 +17,6 @@
 #define SPL_EXPAND(a, b)          SPL_EXPAND2(a, b)
 #define SPL_NAMESPACE(symbol)     SPL_EXPAND(SPL_PFX_, symbol)
 
-#ifdef __cplusplus
-extern "C" {
-#endif
 
 /* SPL interfaces */