ide: remove superfluous SELECT_MASK() call from do_rw_taskfile()

With ->write_devctl method call (which unmasks drive IRQ) preceding
SELECT_MASK() call there is really no need for the latter.

Moreover with the combination of HPT36x controller and the drive on
the quirk_drives[] list this can result in superfluous enable_irq()
call which in turn will trigger WARN() in __enable_irq().

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>