hwspinlock: sprd: fixed warning of unused variable 'sprd_hwspinlock_of_match'

hwspinlock: sprd: fixed warning of unused variable 'sprd_hwspinlock_of_match'

The macro function of_match_ptr() is NULL if CONFIG_OF is not set, in this
case Clang compiler would complain the of_device_id variable is unused.

Reviewed-by: Baolin Wang <baolin.wang7@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Fixes: d8c8bbbb1aba ("hwspinlock: sprd: Add hardware spinlock driver")
Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
Link: https://lore.kernel.org/r/20201112070410.14810-1-zhang.lyra@gmail.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>