drm: bridge: ldb: Drop DE flip from Freescale i.MX8MP LDB bridge

The DE inversion is implemented in LCDIFv3 driver and is no longer
needed in the LDB bridge which does not invert the DE signal. Drop
the inversion.

Fixes: 463db5c2

 ("drm: bridge: ldb: Implement simple Freescale i.MX8MP LDB bridge")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Maxime Ripard <maxime@cerno.tech>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Robby Cai <robby.cai@nxp.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
To: dri-devel@lists.freedesktop.org
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220630174031.92354-1-marex@denx.de