HID: remove 2 unused usb.h includes

These 2 are left over from the USB dependency cleaning, so there is
no need to keep them.

[[e-mail]: fix filename]
Signed-off-by: Benjamin Tissoires <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-multitouch.c

···
 #include <linux/hid.h>
 #include <linux/module.h>
 #include <linux/slab.h>
-#include <linux/usb.h>
 #include <linux/input/mt.h>
 #include <linux/string.h>
 

drivers/hid/hid-steelseries.c

···
  */
 
 #include <linux/device.h>
-#include <linux/usb.h>
 #include <linux/hid.h>
 #include <linux/module.h>