ppc/lopec: remove ppc_ide_md hooks

* Add IDE_HFLAG_FORCE_LEGACY_IRQS host flag for Motorola-LoPEC platform
  to sl82c105 host driver.

* Remove ppc_ide_md hooks from arch/ppc/platforms/lopec.c - no need for
  them (sl82c105 host driver takes care of all this setup).

* Then remove no longer needed <linux/ide.h> include.

Looking at arch/ppc/configs/lopec_defconfig:

...
CONFIG_IDE_GENERIC=y
CONFIG_BLK_DEV_IDEPCI=y
# CONFIG_IDEPCI_SHARE_IRQ is not set
# CONFIG_BLK_DEV_OFFBOARD is not set
CONFIG_BLK_DEV_GENERIC=y
# CONFIG_BLK_DEV_OPTI621 is not set
CONFIG_BLK_DEV_SL82C105=y
...

there should be no functional changes unless somebody preferred to disable
sl82c105 host driver and use only ide_generic one (but why would anybody
want to do such thing :-).

PS It seems that lopec_defconfig hasn't been updated for ages but if somebody
is going to do it please look into disabling IDE_GENERIC and BLK_DEV_GENERIC
config options.  Thanks.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>