MIPS: PowerTV: Removing dead CONFIG_DIAGNOSTICS

CONFIG_DIAGNOSTICS doesn't exist in Kconfig, therefore removing all
references for it from the source code.

Signed-off-by: Christoph Egger <siccegge@cs.fau.de>
To: David VomLehn <dvomlehn@cisco.com>
To: Yoichi Yuasa <yuasa@linux-mips.org>
To: linux-mips@linux-mips.org
To: linux-kernel@vger.kernel.org
Cc: vamos@i4.informatik.uni-erlangen.de
Patchwork: https://patchwork.linux-mips.org/patch/1374/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>