MIPS: IP22/IP28 Disable early printk to fix boot problems on some systems.

Some Debian users have reported that the kernel hangs early during boot on
some IP22 systems.  Thomas Bogendoerfer found that this is due to a "bad
interaction between CONFIG_EARLY_PRINTK and overwritten prom memory during
early boot".  Since there's no fix yet, disable CONFIG_EARLY_PRINTK for now.

Signed-off-by: Martin Michlmayr <tbm@cyrius.com>
Cc: linux-mips@linux-mips.org
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Dmitri Vorobiev <dmitri.vorobiev@gmail.com>
Patchwork: http://patchwork.linux-mips.org/patch/702/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>