docs: fb: Correcting the location of FRAMEBUFFER_CONSOLE option.

fbcon doc mentions FRAMEBUFFER_CONSOLE option to be under
Device Drivers->Graphics Support->Frame buffer Devices->
Console display driver support->Framebuffer Console Support,
while its under Device Drivers->Graphics Support->
Console display driver support->Framebuffer Console Support.

Correcting it in the docs.

Signed-off-by: Bilal Wasim <bilalwasim676@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200824145155.42502-1-bilalwasim676@gmail.com