console/dummy: Move screen size selection from CPP to Kconfig

PA-RISC already handled the dummy console screen size selection in
Kconfig, so generalize this to other platforms.

ARM keeps on using screen_info, which is filled in by
platform-specific code, or from ATAGS.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

diff --cc drivers/video/console/Kconfig
Simple merge

diff --cc drivers/video/console/dummycon.c
Simple merge