Input: da7280 - remove an unused field in struct da7280_haptic

In "struct da7280_haptic", the 'legacy' field is unused.
Remove it.

Found with cppcheck, unusedStructMember.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/ac251b456933bcc6fe297b738f9304bd259185c1.1714539865.git.christophe.jaillet@wanadoo.frSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/da7280.c

@@ -230,7 +230,6 @@ struct da7280_haptic {
 	struct i2c_client *client;
 	struct pwm_device *pwm_dev;
 
-	bool legacy;
 	struct work_struct work;
 	int val;
 	u16 gain;