USB: Refactor hub_port_wait_reset.

Refactor hub_port_wait_reset into a small loop to wait for the port
reset to be complete, and then a larger block to deal with the final
port status.  This patch should not change any current behavior.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>