video: Drop unused console functions

CONFIG_CONSOLE_CURSOR, CONFIG_SYS_CONSOLE_BLINK_COUNT and
CONFIG_CONSOLE_TIME are not used by any board. The implementation is not
great and stands in the way of a refactor of i8042. Drop these for now.
They can be re-introduced quite easily later, perhaps with driver-model
real-time-clock (RTC) support.

When reintroducing, it might be useful to make a few changes:
- Blink time would be more useful than blink count
- The confusing #ifdefs should be avoided
- The time functions should support driver model
- It would be best keyed off console_tstc() or some similar idle loop
    rather than a particular input driver (i8042 in this case)

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>