cfbconsole: Add support for stride != width

cfbconsole currently assumes that the width and stride of the framebuffer
are the same, in most places where stride matters it uses a VIDEO_LINE_LEN
helper macro.

This commit changes the few places not using VIDEO_LINE_LEN to also use
VIDEO_LINE_LEN, and protects the default VIDEO_LINE_LEN with a #ifndef
guard, allowing the boards config.h to override and, and thus support
cases where stride != width.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Anatolij Gustschin <agust@denx.de>