This allows m68k mac systems to switch from the deprecated IDE subsystem
to libata.

This was tested on my Quadra 630. I haven't tested it on my PowerBook 150
because I don't have a RAM adapter board for it. It appears that the
hardware I tested doesn't need macide_clear_irq() or macide_test_irq().
If it did, the generic driver would not have worked. It's possible that
those routines are needed for the PowerBook 150 but we can cross that
bridge if and when we come to it.

BTW, macide_clear_irq() appears to suffer from a race condition. The write
to the interrupt flags register could have unintended side effects as it
may alter other flag bits. Fortunately, all of the other bits are unused
by Linux. When tested on my Quadra 630, the assignment *ide_ifr &= ~0x20
was observed to have no effect on bit 5, so it may be redundant anyway.

Cc: Michael Schmitz <schmitzmic@gmail.com>
Cc: Joshua Thompson <funaho@jurai.org>
Reviewed-by: Michael Schmitz <schmitzmic@gmail.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Link: https://lore.kernel.org/r/11a56b3317df3bb2ddc15fd29b40b6820e9c7444.1623287706.git.fthain@linux-m68k.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>