This errata workaround was introduced for i.MX6Q, i.MX6D and i.MX6SL.
Old revisions of i.MX6s chips had no problems with the PFD resets.

In a newer i.MX6s revision I had issues with this code when booting in
internal boot mode from NAND or in serial downloader mode. FUSE mode
worked fine although it jumped directly to serial downloader mode.

This patch executes the PFD workaround only for i.MX6Q and i.MX6D which
fixes the issues I saw.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>