See function: FLEXSPI_NOR_PreEnterOctalMode
The compiler does not generate a warning or error for this line, but MUCXpresso puts a little yellow '?' icon next to it with the text 'Syntax error'. Thought your MCUXpresso developers would like to know. :-)
This seems to be an error caused by little syntax differences in MCUXpresso parser and compiler. Please see this link for more info and how to disable it.