Support variable length transfers based on SS_N

[markusdd]

I'm having an issue where I wish to capture a long sequence of transfers.
The part suppots variable length transfers, so after command+addr there is a variable amoount of data bytes.
The bad thing is I cannot get these covered with one analyzer, and even get some false positives.
There should be an option to use ss_n as a 'framing'' signal which determines transfer length instead of hardcoding it.

example:

This would also add suppport for e.g. XIP scenarios where SPI or even QSPI devices are put into a burst mode where you can keep pulling out or write in data continuously.