ASoC: cs42l56: Use case range at appropriate place

The readable registers are in continuous range: 0x01 ~ 0x2e.
Use case range syntax makes the code shorter with better readability when
we have a large number of continuous switch cases.
No functional change with this patch.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Brian Austin <brian.austin@cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>