[POWERPC] Fix compilation for CONFIG_DEBUGGER=n and CONFIG_KEXEC=y

Looks like "[POWERPC] kdump shutdown hook support" broke builds when
CONFIG_DEBUGGER=n and CONFIG_KEXEC=y, such as in g5_defconfig:

arch/powerpc/kernel/crash.c: In function 'default_machine_crash_shutdown':
arch/powerpc/kernel/crash.c:388: error: '__debugger_fault_handler' undeclared (first use in this function)
arch/powerpc/kernel/crash.c:388: error: (Each undeclared identifier is reported only once
arch/powerpc/kernel/crash.c:388: error: for each function it appears in.)

Move the debugger hooks to under CONFIG_DEBUGGER || CONFIG_KEXEC, since
that's when the crash code is enabled.

(I should have caught this with my build-script pre-merge, my bad. :( )
Signed-off-by: NOlof Johansson <olof@lixom.net>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/kernel/traps.c

@@ -54,7 +54,7 @@
 #endif
 #include <asm/kexec.h>
 
-#ifdef CONFIG_DEBUGGER
+#if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)
 int (*__debugger)(struct pt_regs *regs);
 int (*__debugger_ipi)(struct pt_regs *regs);
 int (*__debugger_bpt)(struct pt_regs *regs);

include/asm-powerpc/system.h

@@ -65,7 +65,7 @@
 struct task_struct;
 struct pt_regs;
 
-#ifdef CONFIG_DEBUGGER
+#if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)
 
 extern int (*__debugger)(struct pt_regs *regs);
 extern int (*__debugger_ipi)(struct pt_regs *regs);