Avoid LDB and IPU DI clocks both using the same parent. LDB requires
pasthrough clock to avoid breaking timing while IPU DI does not.

Force IPU DI clocks to use IMX6QDL_CLK_PLL2_PFD0_352M as parent
and LDB to use IMX6QDL_CLK_PLL5_VIDEO_DIV.

This fixes an issue where attempting atomic modeset while using
HDMI and display port at the same time causes LDB clock programming
to destroy the programming of HDMI that was done during the same
modeset.

Cc: stable@vger.kernel.org
Signed-off-by: Robert Beckett <bob.beckett@collabora.com>
[Use IMX6QDL_CLK_PLL2_PFD0_352M instead of IMX6QDL_CLK_PLL2_PFD2_396M
 originally chosen by Robert Beckett to avoid affecting eMMC clock
 by DRM atomic updates]
Signed-off-by: Ian Ray <ian.ray@ge.com>
[Squash Robert's and Ian's commits for bisectability, update patch
 description and add stable tag]
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>