[POWERPC] Fix section mismatch in crash_dump.c

WARNING: vmlinux.o(.text+0x23258): Section mismatch: reference to .init.text:.lmb_reserve (between '.reserve_kdump_trampoline' and '.restore_processor_state')

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/crash_dump.c

@@ -25,7 +25,7 @@
 #define DBG(fmt...)
 #endif
 
-void reserve_kdump_trampoline(void)
+void __init reserve_kdump_trampoline(void)
 {
 	lmb_reserve(0, KDUMP_RESERVE_LIMIT);
 }