usb: dwc2: Update port suspend/resume function definitions.

Earlier "dwc2_port_suspend()" and "dwc2_port_resume()" functions
were implemented without proper description and host or device mode
difference.

- Added "dwc2_port_suspend" and "dwc2_port_resume" functions to
  "core.h" header file.

- Updated function description in documentation.

Acked-by: Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>
Signed-off-by: Artur Petrosyan <Arthur.Petrosyan@synopsys.com>
Link: https://lore.kernel.org/r/20210408094502.61D18A0232@mailhost.synopsys.com


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