drm: renesas: rzg2l_mipi_dsi: Move rzg2l_mipi_dsi_set_display_timing()

drm: renesas: rzg2l_mipi_dsi: Move rzg2l_mipi_dsi_set_display_timing()

The RZ/G2L hardware manual (Rev. 1.50, May 2025), Section 34.4.2.1,
requires display timings to be set after the HS clock is started. Move
rzg2l_mipi_dsi_set_display_timing() from
rzg2l_mipi_dsi_atomic_pre_enable() to rzg2l_mipi_dsi_atomic_enable(),
placing it after rzg2l_mipi_dsi_start_hs_clock(). Drop the unused ret
variable from rzg2l_mipi_dsi_atomic_pre_enable().

Fixes: 5ce16c169a4c ("drm: renesas: rz-du: Add atomic_pre_enable")
Fixes: 7a043f978ed1 ("drm: rcar-du: Add RZ/G2L DSI driver")
Cc: stable@vger.kernel.org
Reviewed-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Link: https://patch.msgid.link/20260330104450.128512-2-biju.das.jz@bp.renesas.com
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>