drivers: udc_dwc2: Submit reset after chirp sequence

DWC USB 2.0 HS OTG Controller sets USB Reset interrupt after Reset
signalling starts, but before the High-Speed Detection Handshake. This
allows software to perform most of the reset handling even before the
connection speed is known. The device controller indicates High-Speed
Detection Handshake result is available in DSTS register by setting
Enumeration Done interrupt.

USB stack expects that the connection speed is known immediately after
UDC_EVT_RESET is submitted. Due to this expectation, it is important to
submit UDC_EVT_RESET only after Enumeration Done interrupt to prevent
the USB stack from reading (and storing) actual device speed before
it is known.

Signed-off-by: Tomasz Moń <tomasz.mon@nordicsemi.no>