AxiStreamRingBuffer Bug fix and whitespace removal

[ruck314]

Description

• whitespace removal for a TCL file
• adding AxiStreamRingBufferTb.vhd
• fixed bug in AxiStreamRingBuffer.vhd where not logging data before external trigger
  • Bug discovered by @riku238 during KEK BPM testing

[ruck314]

@jumdz I wrote the simple simulation test bed to confirm that I observe the same behavior that Riku was seeing and verified that it is fixed.