drm/panel: sitronix-st7789v: fix sync flags for t28cp45tn89

drm/panel: sitronix-st7789v: fix sync flags for t28cp45tn89

I planned to set the polarity of horizontal and vertical sync, but
accidentally described vertical sync twice with different polarity
instead.

Note, that there is no functional change, because the driver only
makes use of DRM_MODE_FLAG_P[HV]SYNC to divert from the default
active-low polarity.

Reported-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Closes: https://lore.kernel.org/all/20250923132616.GH20765@pendragon.ideasonboard.com/
Fixes: a411558cc143 ("drm/panel: sitronix-st7789v: add Inanbo T28CP45TN89 support")
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20251001-t28cp45tn89-fix-v2-1-67fe8e3046ca@collabora.com