quota: Remove unused declaration

There is no point in declaring quotactl() syscall prototype in kernel header and
'make headers_check' complains about it. So just remove those lines.
Signed-off-by: Jan Kara <jack@suse.cz>

include/linux/quota.h

@@ -415,13 +415,5 @@ struct quota_module_name {
 	{QFMT_VFS_V0, "quota_v2"},\
 	{0, NULL}}
 
-#else
-
-# /* nodep */ include <sys/cdefs.h>
-
-__BEGIN_DECLS
-long quotactl __P ((unsigned int, const char *, int, caddr_t));
-__END_DECLS
-
 #endif /* __KERNEL__ */
 #endif /* _QUOTA_ */