regulator: pv88060: Fix array out-of-bounds access

Fix off-by-one while iterating current_limits array.
The valid index should be 0 ~ n_current_limits -1.

Fixes: f307a7e9 ("regulator: pv88060: new regulator driver")
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>