MIPS: mark prom_free_prom_memory() everywhere with __init

On OCTEON the function is non-trivial and we can potentially even save
some memory.
Signed-off-by: NAaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: NDavid Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9338/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/cavium-octeon/setup.c

@@ -1049,7 +1049,7 @@ int prom_putchar(char c)
 }
 EXPORT_SYMBOL(prom_putchar);
 
-void prom_free_prom_memory(void)
+void __init prom_free_prom_memory(void)
 {
 	if (CAVIUM_OCTEON_DCACHE_PREFETCH_WAR) {
 		/* Check for presence of Core-14449 fix.  */

arch/mips/lantiq/prom.c

@@ -41,7 +41,7 @@ int ltq_soc_type(void)
 	return soc_info.type;
 }
 
-void prom_free_prom_memory(void)
+void __init prom_free_prom_memory(void)
 {
 }
 

arch/mips/mti-sead3/sead3-init.c

@@ -147,6 +147,6 @@ void __init prom_init(void)
 #endif
 }
 
-void prom_free_prom_memory(void)
+void __init prom_free_prom_memory(void)
 {
 }