USB: Documentation/usb/hotplug.txt: Checkpatch cleanup

Documentation/usb/hotplug.txt:13: ERROR: trailing whitespace
Documentation/usb/hotplug.txt:87: ERROR: trailing whitespace
Signed-off-by: NAndrea Gelmini <andrea.gelmini@gelma.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>