video: cfb_console: fix build warnings

Fix:
cfb_console.c:371: warning: 'cursor_state' defined but not used
cfb_console.c:372: warning: 'old_col' defined but not used
cfb_console.c:373: warning: 'old_row' defined but not used
cfb_console.c:435: warning: 'video_invertchar' defined but not used

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Tested-by: Wolfgang Denk <wd@denx.de>