fbdev: Ditch fb_edid_add_monspecs

It's dead code ever since

commit 34280340


Author: Geert Uytterhoeven <geert+renesas@glider.be>
Date:   Fri Dec 4 17:01:43 2015 +0100

    fbdev: Remove unused SH-Mobile HDMI driver

Also with this gone we can remove the cea_modes db. This entire thing
is massively incomplete anyway, compared to the CEA parsing that
drm_edid.c does.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tavis Ormandy <taviso@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190721201956.941-1-daniel.vetter@ffwll.ch