pulsar_adc: add split transfer functionality

[LBFFilho]

Add a parameter, SPLIT_TRANSFER SIZE to enable split transfers. If SPLIT_TRANSFER is set to 0, split transfers are disabled (previous behavior). If set to any other positive value =an asymetric fifo is used to stitch together 2 transfers before sending them to the DMA. In this case SPLIT_TRANSFER is used to indicate the size of each transfer in the split.

PR Type

• [ ] Bug fix (change that fixes an issue)
• [x] New feature (change that adds new functionality)
• [ ] Breaking change (has dependencies in other repos or will cause CI to fail)

PR Checklist

• [x] I have followed the code style guidelines
• [ ] I have performed a self-review of changes
• [x] I have compiled all hdl projects and libraries affected by this PR
• [ ] I have tested in hardware affected projects, at least on relevant boards
• [ ] I have commented my code, at least hard-to-understand parts
• [x] I have signed off all commits from this PR
• [x] I have updated the documentation (wiki pages, ReadMe files, Copyright etc)
• [x] I have not introduced new Warnings/Critical Warnings on compilation
• [ ] I have added new hdl testbenches or updated existing ones

[sarpadi]

Looks good. Should work as long as the software resets the FIFO properly. I would try using only one build parameter. Either use a fixed width value or use only the SPLIT_SIZE parameter. if SPLIT_SIZE = 0 (default) then the feature is not used at all, if SPLIT_SIZE != 0 then use the value as width or something similar.