USB: Documentation: Use correct character in gadget_hid.txt

Use ASCII minus sign instead of unicode EN DASH in gadget_hid.txt. Also remove
two unecessary spaces in the same file.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/usb/gadget_hid.txt

@@ -97,7 +97,7 @@ Send and receive HID reports
 	HID gadget.
 
 	Another interesting example is the caps lock test. Type
-	-–caps-lock and hit return. A report is then sent by the
+	--caps-lock and hit return. A report is then sent by the
 	gadget and you should receive the host answer, corresponding
 	to the caps lock LED status.