drm/tilcdc: fix raster control register setting

The fdd property of the tilcdc_panel_info structure must set the reqdly
bit field  (bit 12 to 19) of the raster control register. The previous
statement set the least significant bit instead.

Signed-off-by: Dario Binacchi <dariobin@libero.it>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Jyri Sarha <jyri.sarha@iki.fi>
Tested-by: Jyri Sarha <jyri.sarha@iki.fi>
Signed-off-by: Jyri Sarha <jyri.sarha@iki.fi>
Link: https://patchwork.freedesktop.org/patch/msgid/20210216202225.12861-1-dariobin@libero.it