rtc: rv3029: let regmap validate the register ranges

Instead of trying to validate the accessed registers in custom functions,
let regmap handle that. This allows to defines all the holes in the
register range and gives access to the regmap debugfs register dump.

Link: https://lore.kernel.org/r/20191214221022.622482-3-alexandre.belloni@bootlin.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>