[PATCH] kexec: fix warnig of crash_zero_bytes in crash.c

["Tiezhu Yang" <kernelpatch@126.com>]

This patch fixes the following sparse warning:

arch/x86/kernel/crash.c:59:15:
warning: symbol 'crash_zero_bytes' was not declared. Should it be static?

In addition, crash_zero_bytes is used when CONFIG_KEXEC_FILE is
set, so make it only available under CONFIG_KEXEC_FILE. Otherwise,
if CONFIG_KEXEC_FILE is not set, the following warning will appear:

arch/x86/kernel/crash.c:59:22:
warning: ‘crash_zero_bytes’ defined but not used [-Wunused-variable]

Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call")
Signed-off-by: Tiezhu Yang <kernelpatch@126.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
 arch/x86/kernel/crash.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 576b2e1..f13480e 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -56,7 +56,9 @@ struct crash_memmap_data {
  */
 crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss = NULL;
 EXPORT_SYMBOL_GPL(crash_vmclear_loaded_vmcss);
-unsigned long crash_zero_bytes;
+#ifdef CONFIG_KEXEC_FILE
+static unsigned long crash_zero_bytes;
+#endif
 
 static inline void cpu_crash_vmclear_loaded_vmcss(void)
 {
-- 
1.8.3.1