ide: make ide_pc_intr() static

* Always use ide_pc_intr as a handler in ide_pc_intr().

* Remove no longer used ide*_pc_intr() and 'handler'
  argument from ide_{transfer_pc,pc_intr}().

* Make ide_pc_intr() static.

There should be no functional changes caused by this patch.

Cc: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>