Debugging Version: removed irq disabling / enabling in irq handling

  - removed irq disabling / enabling in irq handling
    disabling the irq in at86rf230_isr() and reenabling it in
    at86rf230_irqwork() opens a window, where irqs from the rf230
    could be missed. This results in a hangup of the irq handling,
    because the rf230 resets its irq line only after reading the
    irq status register, which the driver doesn't read since it
    did not dected that interrupt.

  - added some debug output

  - added an extra read of the irq register in at86rf230_hw_init()
    to clear the interrupt register and line from any possible stale
    interrupts
removed second reading of interrupt status register from hw_init function
Merge branch 'rpi-3.6.y-rf230-3.8.0-merge' of github.com:hoerman/linux.rpi into rpi-3.6.y-rf230-3.8.0-merge