drm/bridge: tc358767: Drop line_pixel_subtract

drm/bridge: tc358767: Drop line_pixel_subtract

This line_pixel_subtract is no longer needed now that the bridge can
request and obtain specific pixel clock on input to the bridge, with
clock frequency that matches the Pixel PLL frequency.

The line_pixel_subtract is now always 0, so drop it entirely.

The line_pixel_subtract was not reliable as it never worked when the
Pixel PLL and input clock were off just so that the required amount
of pixels to subtract would not be whole integer.

Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240625120334.145320-3-marex@denx.de