kernel: fix -Wstrict-prototypes warnings/errors

* On newer kernel for some reason -Wno-strict-prototypes still does not fix the errors or warnings.
* To fix it, we just need to add void type.

Signed-off-by: rsuntk <rsuntk@yukiprjkt.my.id>

kernel/kernel_compat.h

@@ -40,7 +40,7 @@ extern long ksu_strncpy_from_user_retry(char *dst,
 extern struct key *init_session_keyring;
 #endif
 
-extern void ksu_android_ns_fs_check();
+extern void ksu_android_ns_fs_check(void);
 extern struct file *ksu_filp_open_compat(const char *filename, int flags,
 					 umode_t mode);
 extern ssize_t ksu_kernel_read_compat(struct file *p, void *buf, size_t count,