ref: gl: psvita: use Cvar_FullSet to disable r_studio_drawelements

ref/gl/gl_studio.c

@@ -152,7 +152,7 @@ void R_StudioInit( void )
 
 #if XASH_PSVITA
 	// don't do the same array-building work twice since that's what our FFP shim does anyway
-	gEngfuncs.Cvar_SetValue( "r_studio_drawelements", 0 );
+	gEngfuncs.Cvar_FullSet( "r_studio_drawelements", "0", FCVAR_READ_ONLY );
 #endif
 
 	Matrix3x4_LoadIdentity( g_studio.rotationmatrix );