If U-Boot build with DEBUG enabled/defined the first call of "debug"
function (that dumps data to any available console) will happen before
zeroing of initial "gd" in init call "zero_global_data" in
"init_sequence_f".

And if stack was not filled with zeros chances are high that
"gd->have_console" won't be 0. In its turn it will cause attempt to
output things to non-initialized yet serial console.

So for safety and predictability we set "gd->have_console = 0".

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Cc: Mischa Jonker <mjonker@synopsys.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>