rtc: pcf85063: return meaningful value for RTC_VL_READ

PCF85063_REG_SC_OS means the voltage dropped too low and data has been
lost.

Link: https://lore.kernel.org/r/20191214220259.621996-12-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
1 file changed