regulator: da9063: Simplify da9063_buck_set_mode for BUCK_MODE_MANUAL case

The sleep flag bit decides the mode for BUCK_MODE_MANUAL case, simplify
the logic as the result is the same.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Link: https://lore.kernel.org/r/20190926055128.23434-2-axel.lin@ingics.com


Signed-off-by: Mark Brown <broonie@kernel.org>