If we need to ensure only one of the buck[2|3|4]_gpiodvs can be specificed,
check them earlier.
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Sangbeom Kim <sbkim73@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>