oprofile, x86: fix init_sysfs() function stub

The use of the return value of init_sysfs() with commit

 10f0412f oprofile, x86: fix init_sysfs error handling

discovered the following build error for !CONFIG_PM:

 .../linux/arch/x86/oprofile/nmi_int.c: In function ‘op_nmi_init’:
 .../linux/arch/x86/oprofile/nmi_int.c:784: error: expected expression before ‘do’
 make[2]: *** [arch/x86/oprofile/nmi_int.o] Error 1
 make[1]: *** [arch/x86/oprofile] Error 2

This patch fixes this.
Reported-by: NIngo Molnar <mingo@elte.hu>
Cc: stable@kernel.org
Signed-off-by: NRobert Richter <robert.richter@amd.com>

arch/x86/oprofile/nmi_int.c

@@ -585,8 +585,10 @@ static void exit_sysfs(void)
 }
 
 #else
-#define init_sysfs() do { } while (0)
-#define exit_sysfs() do { } while (0)
+
+static inline int  init_sysfs(void) { return 0; }
+static inline void exit_sysfs(void) { }
+
 #endif /* CONFIG_PM */
 
 static int __init p4_init(char **cpu_type)