tmc2240: Allow the slope_control field to be configured via printer.cfg

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

Author: KevinOConnor

docs/Config_Reference.md

@@ -3846,6 +3846,7 @@ run_current:
 #driver_SEIMIN: 0
 #driver_SFILT: 0
 #driver_SG4_ANGLE_OFFSET: 1
+#driver_SLOPE_CONTROL: 0
 #   Set the given register during the configuration of the TMC2240
 #   chip. This may be used to set custom motor parameters. The
 #   defaults for each parameter are next to the parameter name in the

klippy/extras/tmc2240.py

@@ -408,6 +408,8 @@ def __init__(self, config):
         set_config_field(config, "tpowerdown", 10)
         #   SG4_THRS
         set_config_field(config, "sg4_angle_offset", 1)
+        #   DRV_CONF
+        set_config_field(config, "slope_control", 0)
 
 def load_config_prefix(config):
     return TMC2240(config)