rtc: rv3032: fix nvram nvmem priv pointer

The nvmem priv pointer is set to rv3032 but the rv3032_nvram_write and
rv3032_nvram_read expect the regmap pointer.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201108223710.1574331-1-alexandre.belloni@bootlin.com