ide: remove XFER_* masks from ide-timing.h

* Check requested xfer mode against xfer modes instead of XFER_* masks
  in ide_timing_compute() and cs5535.c::cs5535_set_speed().

* Remove XFER_[MODE,MWDMA,EPIO,PIO] masks.

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>