regulator: lp8788-buck: Remove buck[1|2]_vout_addr array

The vout address for buck[1|2] can be easily calculated,
thus remote these arrays.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Milo Kim <milo.kim@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>