If the Interrupt Flag (IF) is not set, we should not handle the IRQ:
- the line can be shared with other devices
- it can be a spurious interrupt

To avoid reading twice the status register, the ocores_process() function
expects it to be read by the caller.
Signed-off-by: NFederico Vaga <federico.vaga@cern.ch>
Acked-by: NPeter Korsgaard <peter@korsgaard.com>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>