hpt366: merge HPT37x speedproc handlers

Continue with the driver rewrite:

- move the interrupt twiddling code from the speedproc handlers into the
    init_hwif_hpt366 which allows to merge the two HPT37x speedproc handlers
    into one;

- get rid of in init_hpt366 which solely consists of the duplicate code, then
    fold init_hpt37x() into init_chipset_hpt366();

- fix hpt3xx_tune_drive() to always set the PIO mode requested, not the best
    possible one, change hpt366_config_drive_xfer_rate() accordingly, simplify
    it a bit;

- group all the DMA related code together init_hwif_hpt366(), and generally
    clean up and beautify it.
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>