[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: NRalf Baechle <ralf@linux-mips.org>

arch/mips/sgi-ip22/ip22-mc.c

@@ -47,7 +47,7 @@ struct mem {
 /*
  * Detect installed memory, do some sanity checks and notify kernel about it
  */
-static void probe_memory(void)
+static void __init probe_memory(void)
 {
 	int i, j, found, cnt = 0;
 	struct mem bank[4];