ARM: OMAP: Fix section mismatch warning

Fix

WARNING: vmlinux.o(.text+0x1554c): Section mismatch: reference to
.init.text:reserve_bootmem (between 'omapfb_reserve_sdram' and
'omap_32k_timer_set_mode')
Signed-off-by: Dirk Behme <dirk.behme@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/fb.c

@@ -171,7 +171,7 @@ static int check_fbmem_region(int region_idx, struct omapfb_mem_region *rg,
  * Called from map_io. We need to call to this early enough so that we
  * can reserve the fixed SDRAM regions before VM could get hold of them.
  */
-void omapfb_reserve_sdram(void)
+void __init omapfb_reserve_sdram(void)
 {
 	struct bootmem_data	*bdata;
 	unsigned long		sdram_start, sdram_size;