integration/soc: Wire up the sdirq to the CPU

I am working on testing out the patches from:
 https://github.com/litex-hub/linux/pull/8

These linux patches take advantage of the sdcard interrupt to track when
transfers finish.  However, it seems the interrupt is not being
connected to the CPU.

This patch does that by allowing us to directly register and
EventManager module with the irq handler.

litex/soc/integration/soc.py

@@ -1070,12 +1070,17 @@ class SoC(Module):
                     continue
                 if hasattr(self, name):
                     module = getattr(self, name)
-                    if not hasattr(module, "ev"):
+                    ev = None
+                    if hasattr(module, "ev"):
+                        ev = module.ev
+                    elif isinstance(module, EventManager):
+                        ev = module
+                    else:
                         self.logger.error("EventManager {} in {} SubModule.".format(
                             colorer("not found", color="red"),
                             colorer(name)))
                         raise
-                    self.comb += self.cpu.interrupt[loc].eq(module.ev.irq)
+                    self.comb += self.cpu.interrupt[loc].eq(ev.irq)
                 self.add_constant(name + "_INTERRUPT", loc)
 
         # SoC Infos --------------------------------------------------------------------------------
@@ -1558,6 +1563,8 @@ class LiteXSoC(SoC):
             self.sdirq.mem2block_dma.trigger.eq(self.sdmem2block.irq),
             self.sdirq.cmd_done.trigger.eq(self.sdcore.cmd_event.fields.done)
         ]
+        if self.irq.enabled:
+            self.irq.add("sdirq", use_loc_if_exists=True)
 
         # Debug.
         if software_debug: