ide-generic: remove no longer needed ide_probe_legacy()

There is now a generic solution [ide_generic_check_pci_legacy_iobases()]
so MIPS-specific ide_probe_legacy() is no longer necessary.

Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>