MIPS: Remove "weak" from platform_maar_init() declaration

Weak header file declarations are error-prone because they make every
definition weak, and the linker chooses one based on link order (see
10629d71

 ("PCI: Remove __weak annotation from pcibios_get_phb_of_node
decl")).

platform_maar_init() is defined in:

  - arch/mips/mm/init.c (where it is marked "weak")
  - arch/mips/mti-malta/malta-memory.c (without annotation)

The "weak" attribute on the platform_maar_init() extern declaration applies
to the platform-specific definition in arch/mips/mti-malta/malta-memory.c,
so both definitions are weak, and which one we get depends on link order.

Remove the "weak" attribute from the declaration.  That makes the malta
definition strong, so it will always be preferred if it is present.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: linux-mips@linux-mips.org
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/10682/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>