Fix possible buffer overflow in computeDshotDMA function - #300

@AlkaMotors, any thoughts on this PR when you have a moment?

looks good.. i will merge this before the next release. The programming instructions are missing the first step. The command to enter the mode should be here too.
The function can be called by other parts of the code. not just in main.c
I would prefer to not have the function description at all here. Then there are two parts we have to maintain if changes are made but if its helpful and short then its ok. we don't need to repeat the dshot specifications here really.

looks good.. i will merge this before the next release. The programming instructions are missing the first step. The command to enter the mode should be here too. The function can be called by other parts of the code. not just in main.c I would prefer to not have the function description at all here. Then there are two parts we have to maintain if changes are made but if its helpful and short then its ok. we don't need to repeat the dshot specifications here really.

Thank you for feedback.
Added step 0 and removed from doc comment everything else shortening it to bare minimum.