watchdog: sprd: check busy bit before new loading rather than after that

As the specification described, users must check busy bit before start
a new loading operation to make sure that the previous loading is done
and the device is ready to accept a new one.

[ chunyan: Massaged changelog ]

Fixes: 47760346 ("watchdog: Add Spreadtrum watchdog driver")
Signed-off-by: Lingling Xu <ling_ling.xu@unisoc.com>
Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20201029023933.24548-3-zhang.lyra@gmail.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>