usb: dwc2: host: create a function to handle port_resume

port resume sequence may be used in different places. Create a
function to handle it. Make hprt0 read-modify-write atomic and
clear HPRT0_SUSP for both writes as it is a "read, write-set,
and self-clear (R_WS_SC)" bit. Since the lock is released
between the writes, read hprt0 again.

Since the phy clock is stopped in dwc2_port_suspend(), enable it
here and remove the PCGCTL write from dwc2_hcd_hub_control()

Signed-off-by: Gregory Herrero <gregory.herrero@intel.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@intel.com>
Tested-by: Robert Baldyga <r.baldyga@samsung.com>
Tested-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Tested-by: John Youn <johnyoun@synopsys.com>
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>