net: davinci_emac: Fix rollback of emac_dev_open()

If an error occurs during the initialization in emac_dev_open() (the
driver's ndo_open function), interrupts, DMA descriptors etc. must be freed.
The current rollback code is buggy in several ways.

  1) Freeing the interrupts. The current code will not free all interrupts
     that were requested by the driver. Furthermore,  the code tries to do a
     platform_get_resource(priv->pdev, IORESOURCE_IRQ, -1) in its last
     iteration.

     This patch fixes these bugs.

  2) Wrong order of err: and rollback: labels. If the setup of the PHY in
     the code fails, the interrupts that have been requested before are
     not freed:

        request irq
                if requesting irqs fails, goto rollback
        setup phy
                if phy setup fails, goto err
        return 0

     rollback:
        free irqs
     err:

     This patch brings the code into the correct order.

  3) The code calls napi_enable() and emac_int_enable(), but does not
     undo both in case of an error.

     This patch adds calls of emac_int_disable() and napi_disable() to the
     rollback code.

  4) RX DMA descriptors are not freed in case of an error: Right before
     requesting the irqs, the function creates DMA descriptors for the
     RX channel. These RX descriptors are never freed when we jump to either
     rollback or err.

     This patch adds code for freeing the DMA descriptors in the case of
     an initialization error. This required a modification of
     cpdma_ctrl_stop() in davinci_cpdma.c: We must be able to call this
     function to free the DMA descriptors while the DMA channels are
     in IDLE state (before cpdma_ctlr_start() was called).

Tested on a custom board with the Texas Instruments AM1808.

Signed-off-by: Christian Riesch <christian.riesch@omicron.at>
Signed-off-by: David S. Miller <davem@davemloft.net>