ce4100: fix a build error

Fix a build error. CE4100 with no serial errors because the alternate
function is only a prototype not a null function as intended.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/platform/ce4100/ce4100.c

@@ -109,7 +109,7 @@ static __init void sdv_serial_fixup(void)
 }
 
 #else
-static inline void sdv_serial_fixup(void);
+static inline void sdv_serial_fixup(void) {};
 #endif
 
 static void __init sdv_arch_setup(void)