ide: remove set but not used variable 'hwif'

Fix the following gcc warning:

drivers/ide/pmac.c: In function pmac_ide_setup_device:
drivers/ide/pmac.c:1027:14: warning: variable hwif set but not used
[-Wunused-but-set-variable]

Fixes: d58b0c39

 ("powerpc/macio: Rework hotplug media bay support")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>