[MIPS] PNX: Fix modpost warnings.

  MODPOST vmlinux
WARNING: arch/mips/philips/pnx8550/common/built-in.o(.text+0xd40): Section mismatch: reference to .init.data: (after 'pnx8550_platform_init')
WARNING: arch/mips/philips/pnx8550/common/built-in.o(.text+0xd44): Section mismatch: reference to .init.data: (after 'pnx8550_platform_init')

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