drm/bridge: cdns-dsi: Update htotal in cdns_dsi_mode2cfg()

drm/bridge: cdns-dsi: Update htotal in cdns_dsi_mode2cfg()

cdns_dsi_mode2cfg() calculates the dsi timings, but for some reason
doesn't set the htotal based on those timings. It is set only later, in
cdns_dsi_adjust_phy_config().

As cdns_dsi_mode2cfg() is the logical place to calculate it, let's move
it there. Especially as the following patch will remove
cdns_dsi_adjust_phy_config().

Reviewed-by: Aradhya Bhatia <aradhya.bhatia@linux.dev>
Tested-by: Parth Pancholi <parth.pancholi@toradex.com>
Tested-by: Jayesh Choudhary <j-choudhary@ti.com>
Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
Link: https://lore.kernel.org/r/20250723-cdns-dsi-impro-v5-8-e61cc06074c2@ideasonboard.com
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>