drm: rcar-du: lvds: Rename PLLEN bit to PLLON

drm: rcar-du: lvds: Rename PLLEN bit to PLLON

BugLink: http://bugs.launchpad.net/bugs/1714298
commit 82e7c5e4964545352accff4b44bbcaa2c38e7fc1 upstream.

The bit is named PLLON in the datasheet, rename it.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Thong Ho <thong.ho.px@rvc.renesas.com>
Signed-off-by: Nhan Nguyen <nhan.nguyen.yb@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>