regulator: mcp16502: remove void documentation of struct mcp16502

struct mcp16502 has no members called rdev or rmap. Remove the
documentation.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/1605280870-32432-7-git-send-email-claudiu.beznea@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>