Revert "tty: serial: 8250: add CON_CONSDEV to flags"

This commit needs to be reverted because it prevents people from
using the serial console as a secondary console with input being
directed to tty0.

IOW, if you boot with console=ttyS0 console=tty0 then all kernels
prior to this commit will produce output on both ttyS0 and tty0
but input will only be taken from tty0.  With this patch the serial
console will always be the primary console instead of tty0,
potentially preventing people from getting into their machines in
emergency situations.

Fixes: d03516df ("tty: serial: 8250: add CON_CONSDEV to flags")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>