host: cal: Align waveform start addresses with DRAM

In the X420 IQ/DC offset compensation, waveforms get preloaded into the
DRAM. During the measurement they are then streamed to the radio. The
DRAM on the device operates at 4k boundaries. Therefore, the waveform
start addresses are rounded up to the next multiple of 4096 bytes to
ensure proper alignment and avoid potential underflows during playback.

host/python/uhd/usrp/cal/iq_dc_compensation.py

@@ -680,6 +680,14 @@ class HBXCompensator:
                 f"Waveform size {waveform_num_bytes} bytes is not aligned with the word size "
                 f"{txs[channels[0]].word_size} bytes. Please adjust the number of samples."
             )
+
+        # The DRAM on the device is operating at 4k boundaries. Therefore, the
+        # waveform start addresses are rounded up to the next multiple of 4096
+        # bytes to ensure proper alignment and avoid potential issues during
+        # playback.
+        alignment = 4096
+        waveform_num_bytes = ((waveform_num_bytes + alignment - 1) // alignment) * alignment
+
         # check the total required memory for all waveforms against the
         # available memory on the device
         if self._args.tx: