rtc: rv8803: simplify the return expression of rv8803_nvram_write

Simplify the return expression.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200921082449.2591981-1-liushixin2@huawei.com