in case of i2c is busy a true is now returned (buserror)
added option to pass len=o to read/write methods of i2c

OTP bit was 0 instead of of 1<<0 i.e. 0x01

First debug session: the dmp seems to produce outputs in the fifo now but:
there is still an issue with the read multiple bytes i2c methos
would require another fix.