[PATCH] x86/irqflags: provide a declaration for native_save_fl

[Nick Desaulniers]

Fixes commit d0a8d9378d16 ("x86/paravirt: Make native_save_fl() extern
inline").

It was reported that the above commit was causing users of gcc < 4.9 to
observe -Werror=missing-prototypes errors.

Indeed, it seems that:
extern inline unsigned long native_save_fl(void) { return 0; }

compiled with -Werror=missing-prototypes produces this warning in gcc <
4.9, but not gcc >= 4.9.

Cc: stable@xxxxxxxxxxxxxxx # 4.17, 4.14, 4.9, 4.4
Reported-by: David Laight <david.laight@xxxxxxxxxx>
Reported-by: Jean Delvare <jdelvare@xxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
 arch/x86/include/asm/irqflags.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index c4fc17220df9..c14f2a74b2be 100644
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -13,6 +13,8 @@
  * Interrupt control:
  */
 
+/* Declaration required for gcc < 4.9 to prevent -Werror=missing-prototypes */
+extern inline unsigned long native_save_fl(void);
 extern inline unsigned long native_save_fl(void)
 {
 	unsigned long flags;
-- 
2.18.0.597.ga71716f1ad-goog