sparc: fix led.c driver when PROC_FS is not enabled

Fix Sparc build when CONFIG_PROC_FS is not enabled.

Fixes this build error:
arch/sparc/kernel/led.c:107:30: error: 'led_proc_ops' defined but not used [-Werror=unused-const-variable=]
     107 | static const struct proc_ops led_proc_ops = {
         |                              ^~~~~~~~~~~~
   cc1: all warnings being treated as errors

Fixes: 97a32539

 ("proc: convert everything to "struct proc_ops"")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Lars Kotthoff <metalhead@metalhead.ws>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>