drivers: udc_nrf: Remove duplicate endpoint state

Use UDC endpoint state instead of the legacy hal state. Only functional
change relates to overload condition (buffer is too small to hold data
received on OUT endpoint). Previously the data would be completely
discarded and udc driver error would occur (overload event was
unhandled). Now buffer too small error is logged and as much data as
possible is copied to buffer.

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