pdc202xx_old: always enable burst mode

Alan has noticed that distros always enabled burst mode
(+ datasheet confirms that it is the right thing to do).

Thus fix pdc202xx_old host driver to do it unconditionally
and remove no longer needed CONFIG_PDC202XX_BURST option.

Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>