MIPS: bmips: remove unnecessary call to register "simple-bus"

The DT core will register "simple-bus" by default, so it is not necessary
for arch specific code to do so unless there are custom match entries,
auxdata or parent device. Neither of those apply here, so remove the call.

Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@linux-mips.org
Signed-off-by: Rob Herring <robh@kernel.org>
Patchwork: https://patchwork.linux-mips.org/patch/19590/
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-kernel@vger.kernel.org