hwspinlock: sprd: use module_platform_driver() instead postcore initcall

The hardware spinlock devices are defined in the DT, there's no need for
init calls order, remove boilerplate code by using module_platform_driver.

Reviewed-by: Baolin Wang <baolin.wang7@gmail.com>
Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
Link: https://lore.kernel.org/r/20201030034654.15775-3-zhang.lyra@gmail.com


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>