MIPS: malta: Use generic platform_maar_init

The default implementation of platform_maar_init is sufficient for Malta
boards where we want to allow speculation in the regions of memory
corresponding to DDR & disallow it elsewhere. Drop the custom
implementation such that the default is used, reducing the duplication
of information provided by the Malta platform code.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/10677/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>