There is no option (in PSoC Creator)/ Flash API to 'Erase the Entire Flash'. However, there are APIs to perform the row level operation. Please refer the system reference guide ( Open PSoC Creator -> Help-> System Reference Guide ).
Using the PSoC Programmer to erase the chip would be more effective, as I believe you can do what you are asking in that software.
(There is no identical operation/button inside the PSoC Creator IDE however as gyan stated)