fix(hw): broaden assert_rx_capture_valid candidate matching

bq's ADRV9371+ZC706 design exposes neither ``axi-ad9371-rx-hpc``
nor ``axi-ad9371-rx-obs-hpc`` (the adjacent IIO-device-present
assertion in that test uses a permissive
``any("9371" in n or "adrv9" in n.lower())`` pattern precisely
because the buffered-frontend name varies by design).

When none of the explicit ``device_candidates`` match, fall back
to the first IIO device on the context that advertises at least
one non-output scan channel.  Every buffered AXI ADC frontend
registers one, so this recovers cleanly without needing per-board
name plumbing.  Assertion failures now also print the full list
of present devices, so any remaining mismatch is obvious at a
glance.

Author: tfcollins

test/hw/hw_helpers.py

@@ -567,12 +567,31 @@ def assert_rx_capture_valid(
         (device_candidates,) if isinstance(device_candidates, str) else tuple(device_candidates)
     )
     dev = next((d for d in (ctx.find_device(n) for n in candidates) if d is not None), None)
+    if dev is None or not any(c.scan_element and not c.output for c in dev.channels):
+        # No named candidate matched — fall back to the first IIO device
+        # on the context that advertises RX scan channels.  Every buffered
+        # AXI ADC frontend registers them; this handles designs where the
+        # converter's IIO device is called something unexpected (e.g.
+        # ``axi-ad9371-rx-obs-hpc`` when only ``obs`` exists).
+        dev = next(
+            (
+                d
+                for d in ctx.devices
+                if d.name
+                and any(c.scan_element and not c.output for c in d.channels)
+            ),
+            None,
+        )
+    all_names = sorted(d.name for d in ctx.devices if d.name)
     assert dev is not None, (
-        f"No candidate IIO device found{suffix}. Tried: {list(candidates)}"
+        f"No RX-capable IIO device found{suffix}. "
+        f"Tried: {list(candidates)}. Present: {all_names}"
     )
 
     scan_channels = [c for c in dev.channels if c.scan_element and not c.output]
-    assert scan_channels, f"No RX scan channels on {dev.name!r}{suffix}"
+    assert scan_channels, (
+        f"No RX scan channels on {dev.name!r}{suffix}. Present: {all_names}"
+    )
 
     buf = None
     try: