USB: usbfs: Add a capability flag for runtime suspend

The recent commit 7794f486 ("usbfs: Add ioctls for runtime power
management") neglected to add a corresponding capability flag.  This
patch rectifies the omission.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Mayuresh Kulkarni <mkulkarni@opensource.cirrus.com>

Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1908131613490.1941-100000@iolanthe.rowland.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>