HWA: avoid constant suspend and resume on the root hub

Prevent the USB core from suspending the HWA root hub since bus_suspend
and bus_resume are not yet supported.  Otherwise the PM system will chew
up CPU time constantly attempting to suspend and resume the root hub but
never succeeding.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>