Currently it is not possible to have HDMI and LVDS working simultaneously,
because both ports try to use PLL5.

Move the LVDS clock parent to PLL3_USB_OTG, so that HDMI and LVDS can be
driven from independent sources.

With this change the LDB pixel clock goes to 68.57 MHz, which is still
within the valid range for the displays supported by the Ventana boards.
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>