ipu_src_rect_width() was introduced to support odd screen resolutions
such as 1366x768 by internally rounding up primary plane width to a
multiple of 8 and compensating with reduced horizontal blanking.
This also caused overlay plane width to be rounded up, which was not
intended. Fix overlay plane width by limiting the rounding up to the
primary plane.

drm_rect_width(&new_state->src) >> 16 is the same value as
drm_rect_width(dst) because there is no plane scaling support.

Fixes: 94dfec48 ("drm/imx: Add 8 pixel alignment fix")
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Link: https://lore.kernel.org/r/20221108141420.176696-1-p.zabel@pengutronix.deSigned-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20221108141420.176696-1-p.zabel@pengutronix.deTested-by: Ian Ray <ian.ray@ge.com>
(cherry picked from commit 4333472f)
Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>