This change allows the same heap allocation rules to be used when using
malloc regardless if the board has SPRAM or normal RAM.
Integrating with the esp32-camera for example requires that ESP32 SPRAM be
allocatable using the esp-idf capabilities aware allocation functions. In
the case of esp32-camera it's for the framebuffer.
Detect when CONFIG_SPIRAM_USE_MALLOC is in use and use the standard
automatic configuration of leaving 1/2 of the SPRAM available to other
FreeRTOS tasks.
eae2e3516c