instant boot (#1910)

no more boot time :P

python/__init__.py

@@ -304,6 +304,10 @@ class Panda:
     for bus in range(PANDA_BUS_CNT):
       self.set_can_speed_kbps(bus, self._can_speed_kbps)
 
+  @property
+  def spi(self) -> bool:
+    return isinstance(self._handle, PandaSpiHandle)
+
   @classmethod
   def spi_connect(cls, serial, ignore_version=False):
     # get UID to confirm slave is present and up