regulator: mcp16502: add linear_min_sel

Selectors b/w zero and VDD_LOW_SEL are not valid. Use linear_min_sel.

Fixes: 919261c0

 ("regulator: mcp16502: add regulator driver for MCP16502")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/1605280870-32432-4-git-send-email-claudiu.beznea@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>