MIPS: generic: remove unnecessary of_platform_populate call

The DT core will call of_platform_populate, so it is not necessary for
arch specific code to call it unless there are custom match entries,
auxdata or parent device. Neither of those apply here, so remove the call.

Cc: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
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/19591/
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-kernel@vger.kernel.org