- Move IRQ functions from drm_dma.h to new drm_irq.h and disentangle them

    from __HAVE_DMA. This will be useful for adding vblank sync support to
    sis and tdfx. Rename dma_service to irq_handler, which is more
    accurately what it is.
- Fix the #if _HAVE_DMA_IRQ in radeon, r128, mga, i810, i830, gamma to have
    the right number of underscores. This may have been a problem in the
    case that the server died without doing its DRM_IOCTL_CONTROL to
    uninit.