usb: dwc2: Fix partial power down exiting by system resume

usb: dwc2: Fix partial power down exiting by system resume

Fixes the implementation of exiting from partial power down
power saving mode when PC is resumed.

Added port connection status checking which prevents exiting from
Partial Power Down mode from _dwc2_hcd_resume() if not in Partial
Power Down mode.

Rearranged the implementation to get rid of many "if"
statements.

NOTE: Switch case statement is used for hibernation partial
power down and clock gating mode determination. In this patch
only Partial Power Down is implemented the Hibernation and
clock gating implementations are planned to be added.

Fixes: 6f6d70597c15 ("usb: dwc2: bus suspend/resume for hosts with DWC2_POWER_DOWN_PARAM_NONE")
Cc: <stable@vger.kernel.org>
Acked-by: Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>
Signed-off-by: Artur Petrosyan <Arthur.Petrosyan@synopsys.com>
Link: https://lore.kernel.org/r/20210408094607.1A9BAA0094@mailhost.synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>