Add channel mask for add-c port in gemmx

[xiaoling-yi]

In this PR, we add the support for the channel musk for gemmx's add-c support:

• add the channel musk cfg in the hw hjson file and supporting parsing logic for this parameter, including in the streamer_csr_num cal in snax_gen and the streamer para template etc
• add the channel musk for add-c in the sw test
• clean the CSR pass mechanism in the streamer

[jorendumoulin]

Hi, looking good!

I just have two questions:

- the name configurable_channel, seems very unclear. Does has_broadcast make more sense? As in the streamer allows to broadcast the input of one tcdm port to all ports? - Do we need to add an extra csr? Can't we just enable the broadcast by programming 0 to spatialstride? (=every port fetches the same data, so broadcast must be enabled, and channels masked)

edit: i misunderstood still, the naming is a bit confusing. has_channel_mask makes much more sense to me

[xiaoling-yi]

has_channel_mask makes much more sense to me

The parameter name is a historical legacy. I will discuss it with Yunhao to see how to solve it.