Revert "Add board_pre_console_putc to deal with early console output"

This reverts commit 295d3942.

It turns that this really doesn't work very nicely. Instead we should
have a pre-console panic function so that we know that further execution
is impossible and we don't need to worry about trampling on UARTs, etc.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Wolfgang Denk <wd@denx.de>