drivers: udc_dwc2: Fix timeouts when disabling endpoints

Do not set NAK bit again for endpoints that already have NAK bit set.
Do not wait for OUT endpoint 0 disable because it cannot be disabled by
application (DOEPCTL0 EPDis bit is Read-Only).

Disable endpoints before disabling interrupts because it is necessary to
handle RXFLVL interrupt (in Slave mode) for GOUTNAKEFF to become active.

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