Add sil_iowrite{8,16,32}() and sil_ioread{8,16}() helpers, then use them to
merge code accessing configuration registers through PCI and MMIO together.

[ because of this SATA initialization bits from setup_mmio_siimage() are
  moved to init_chipset_siimage() ]

This also cuts code size a bit:

   text    data     bss     dec     hex filename
   4437     164       0    4601    11f9 drivers/ide/pci/siimage.o.before
   3979     164       0    4143    102f drivers/ide/pci/siimage.o.after

While at it:

* Use I/O ops directly instead of using ->IN{B,W} and ->OUT{B,W}.

* Fixup CodingStyle in setup_mmio_siimage().

* Rename 'tmpbyte' variable to 'tmp' in init_chipset_siimage().

There should be no functional changes caused by this patch.
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>