[MIPS] IP22: Fix modpost warning.

  MODPOST vmlinux.o
WARNING: vmlinux.o(.text+0xc70): Section mismatch: reference to .init.text:add_memory_region (between 'probe_memory' and 'enable_local0_irq')

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