drm/bridge: samsung-dsim: Fix porch calcalcuation rounding

The VFP, HBP, and HSA are divided between the available lanes if
there is more than one lane.  For certain timings and lane
configurations, the HFP may not be evenly divisible. If the HFP
is rounded down, it ends up being too small which can cause some
monitors to not sync properly. In these instances, adjust htotal
and hsync to round the HFP up, and recalculate the htotal.

This allows 720P-60 to operation on an i.MX8MP with a four-lane
configuration.

Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de> # Kontron BL i.MX8MM with HDMI monitor
Signed-off-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240601144103.198299-2-aford173@gmail.com