Fix #13445

* Remove duplicate calls to PrepareSector

Some flash memory API calls require that a call to `PrepareSector` is done before use. However this call is already made by the LPC1768 framework so the calls in this code are not required.

* Ensure correct alignment of RAM buffer

The LPC176X flash API requires that the RAM buffer used for write operations must be word-aligned. This change ensures that this is the case.

* Add traceback after watchdog timeout

Add the cpability to perform a traceback following a watchdog timeout.

* Enhanced hardware SPI

Allow use of either SSP0 or SSP1.
Ensure that no data is left in I/O buffers after calls to enable sharing of SSP hardware.

* Make flash emulation of eeprom the default

Make use of flash for eeprom storage the default. This means that usage of eeprom will not cause USB drive mount/unmount operations.

* Allow sharing of SD card

SD card I/O operations from the USB stack take place in idle loop, rather than at interrupt time. Allowing sharing of the SPI bus.

New configuration options to allow usage of the SD card to be specified.

* Fix problem with hardware SPI pins

Use a sector of the LPC flash memory to emulate EEPROM storage, removing the need to have an SD card to store system parameters.