USB: update Kconfig entry for USB_SUSPEND

This patch (as1039) updates the Kconfig entry for USB_SUSPEND.  The
out-of-date reference to "power/state" is fixed, autosuspend is
mentioned, and the dependency on EXPERIMENTAL is removed.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>