use existing spi baudrate instead of hardcoded

Author: FoamyGuy

adafruit_tlc5947.py

@@ -158,7 +158,7 @@ def write(self):
             # Lock the SPI bus and configure it for the shift register.
             while not self._spi.try_lock():
                 pass
-            self._spi.configure(baudrate=1000000, polarity=0, phase=0, bits=8)
+            self._spi.configure(baudrate=self._spi.frequency, polarity=0, phase=0, bits=8)
             # First ensure latch is low.
             self._latch.value = False
             # Write out the bits.