Bluetooth: hci_bcm: Fix unwanted error reporting if no bcm dev
The hci_bcm proto is able to operate without bcm platform device linked
to its uart port. In that case, firmware can be applied, but there is
no power operation (no gpio/irq resources mgmt).
However, the current implementation breaks this use case because of
reporting a ENODEV error in the bcm setup procedure if bcm_request_irq
fails (which is the case if no bcm device linked).
Fix this by removing bcm_request_irq error forwarding.