mfd: da9062: Use MFD_CELL_OF macro

Use MFD_CELL_OF macro helper instead of plain struct properties, which makes
the code a bit shorter and to have commonly defined MFD cell attributes.

Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Acked-by: Adam Ward <DLG-Adam.Ward.opensource@dm.renesas.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230309092254.56279-1-cniedermaier@dh-electronics.com