net/smc: fix compile warning for smc_sysctl

Fix build:

   In file included from net/smc/smc_sysctl.c:17:
>> net/smc/smc_sysctl.h:23:5: warning: no previous prototype \
	for function 'smc_sysctl_init' [-Wmissing-prototypes]
   int smc_sysctl_init(void)
       ^

and

>> WARNING: modpost: vmlinux.o(.text+0x12ced2d): Section mismatch \
in reference from the function smc_sysctl_exit() to the variable
.init.data:smc_sysctl_ops
The function smc_sysctl_exit() references
the variable __initdata smc_sysctl_ops.
This is often because smc_sysctl_exit lacks a __initdata
annotation or the annotation of smc_sysctl_ops is wrong.

Fixes: 462791b ("net/smc: add sysctl interface for SMC")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Dust Li <dust.li@linux.alibaba.com>

net/smc/smc_sysctl.c

@@ -69,12 +69,12 @@ static struct pernet_operations smc_sysctl_ops __net_initdata = {
 	.exit = smc_sysctl_exit_net,
 };
 
-int __init smc_sysctl_init(void)
+int __net_init smc_sysctl_init(void)
 {
 	return register_pernet_subsys(&smc_sysctl_ops);
 }
 
-void smc_sysctl_exit(void)
+void __net_exit smc_sysctl_exit(void)
 {
 	unregister_pernet_subsys(&smc_sysctl_ops);
 }

net/smc/smc_sysctl.h

@@ -20,12 +20,12 @@ void smc_sysctl_exit(void);
 
 #else
 
-int smc_sysctl_init(void)
+static inline int smc_sysctl_init(void)
 {
 	return 0;
 }
 
-void smc_sysctl_exit(void) { }
+static inline void smc_sysctl_exit(void) { }
 
 #endif /* CONFIG_SYSCTL */