optional crc for flash writing

optional crc for flash writing

crc check was always performed on newly flashed data, now it is optional
flash mem can be locked by writing a specific word to a specific address in flash.
to verify flash, target must be halted, and this will (when the new halt sequence is implemented) require reseting the chip. if the target is reset after writing the lock words, then it will lock, hence the CRC will fail because it is not possible to read stuff from the target.

also added a function that resets the jtag state machine.
this is not used yet, but will be soon.
it is implemented to allow strict control over JTAG state machine, necessary to implement to halt and unlocking sequences.