Fix copy/paste error reported in adafruit#3.

This was previously fixed in adafruit#4, but it looks like the fix got clobbered when the LUT code was split out to a separate file.

Author: stoklund

adafruit_emc2101/emc2101_lut.py

@@ -209,7 +209,7 @@ def pwm_frequency(self):
     def pwm_frequency(self, value):
         if value < 0 or value > 0x1F:
             raise AttributeError("pwm_frequency must be from 0-31")
-        self._pwm_freq_div = value
+        self._pwm_freq = value
 
     @property
     def pwm_frequency_divisor(self):