lcd: replace CONSOLE_(ROWS|COLS) with variables

Replace CONSOLE_(ROWS|COLS) macros with variables, and assign the
original macro values.

This is a preparatory step for extracting lcd console code into its own
file.

Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Cc: Anatolij Gustschin <agust@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>