sx1509: Minor cleanup - don't default print_time to 0

It's not valid to use a print_time=0, and it isn't actually used in
the sx1509 code.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/extras/sx1509.py

@@ -81,7 +81,7 @@ class SX1509(object):
             self.reg_dict[reg] = value
         elif reg in self.reg_i_on_dict:
             self.reg_i_on_dict[reg] = value
-    def send_register(self, reg, print_time=0):
+    def send_register(self, reg, print_time):
         data = [reg & 0xFF]
         if reg in self.reg_dict:
             # Word