utils: Fix documentation. 3+3=6 digits equals 3 bytes, not 6

Change-Id: I2722d788a69976e1c64a9caf6cf3049af27f9a30
diff --git a/pySim/utils.py b/pySim/utils.py
index 8463581..43d52dd 100644
--- a/pySim/utils.py
+++ b/pySim/utils.py
@@ -77,7 +77,7 @@
 	return swap_nibbles(rpad(iccid, 20))
 
 def enc_plmn(mcc, mnc):
-	"""Converts integer MCC/MNC into 6 bytes for EF"""
+	"""Converts integer MCC/MNC into 3 bytes for EF"""
 	return swap_nibbles(lpad('%d' % mcc, 3) + lpad('%d' % mnc, 3))
 
 def dec_spn(ef):