Parse out U5xx packages.

Avoid barfing if we're not yet parsing DMA, because we aren't for GPDMA.

parse.py

@@ -585,6 +585,7 @@ def chip_name_from_package_name(x):
         ('(STM32L5....).x[PQ]', '\\1'),
         ('(STM32L0....).xS', '\\1'),
         ('(STM32H7....).xQ', '\\1'),
+        ('(STM32U5....).xQ', '\\1'),
         ('(STM32......).x', '\\1'),
     ]
 
@@ -1074,6 +1075,7 @@ def parse_chips():
             core['dma_channels'] = chs
 
             # Process peripheral - DMA channel associations
+            if chip_dma is not None:
                 for pname, p in peris.items():
                     if (peri_chs := dma_channels[chip_dma]['peripherals'].get(pname)) is not None:
                         p['dma_channels'] = {