Partial refresh hangs/freezes if SRCS is given

[sidju]

• Arduino board: Unexpected Maker FeatherS3

• Display: ThinkInk_154_Tricolor_z90

• Arduino IDE version: 1.8.19

• List the steps to reproduce the problem below:
  Construct a ThinkInk_154_Tricolor_z90 object with HW SPI and all pins given, call begin() on it, call displayPartial() on it. That last function call will never return and the whole processor seems to lock up (serial connection drops).
  (This is confirmed with the partial example.)

Presumably this is related to #35, considering that same as described there it doesn't hang if SRCS is not given (given as -1). But that issue's suggested solution to the SPI deadlock has been applied and disabling HAL locks (a config in the esp32 SDK) made no difference... Furthermore, even without SRCS the partial refresh doesn't affect the display in any perceivable way; so there is most likely a deeper issue here.

As I don't have a proper debugger I can't identify exactly where it locks up, but I hope you can figure this out on your end.

[sidju]

Actually, src/Adafruit_MCPSRAM.cpp seems to still have the same potential deadlock on esp32 as issue #35 refers to.