[MIPS] TXx9: Random cleanup

* Random cleanups spotted by checkpatch script.
* Do not initialize panic_timeout.  "panic=" kernel parameter can be used.
* Do not add "ip=any" or "ip=bootp".  This options is not board specific.
* Do not add "root=/dev/nfs".  This is default on CONFIG_ROOT_NFS.
* Kill unused error checking.
* Fix IRQ comment to match current code.
* Kill some unneeded includes
* ST0_ERL is already cleared in generic code.
* conswitchp is initialized generic code.
* __init is not needed in prototype.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>